fix: Make sessionCount required for batchCreateSessions.

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/Spanner/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:0f66008f69061ea6d41499e2a34da3fc64fc7c9798077e3a37158653a135d801
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/spanner/artman_spanner.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/php/google-cloud-spanner-v1.
synthtool > Running generator for google/spanner/admin/database/artman_spanner_admin_database.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/php/google-cloud-spanner-admin-database-v1.
synthtool > Running generator for google/spanner/admin/instance/artman_spanner_admin_instance.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/php/google-cloud-spanner-admin-instance-v1.
synthtool > Replaced "'serviceAddress' =>" in src/Admin/Instance/V1/Gapic/InstanceAdminGapicClient.php.
synthtool > Replaced "'serviceAddress' =>" in src/Admin/Database/V1/Gapic/DatabaseAdminGapicClient.php.
synthtool > Replaced "'serviceAddress' =>" in src/V1/Gapic/SpannerGapicClient.php.
synthtool > Replaced '@type string \\$serviceAddress\\n\\s+\\*\\s+The address' in src/Admin/Instance/V1/Gapic/InstanceAdminGapicClient.php.
synthtool > Replaced '@type string \\$serviceAddress\\n\\s+\\*\\s+The address' in src/Admin/Database/V1/Gapic/DatabaseAdminGapicClient.php.
synthtool > Replaced '@type string \\$serviceAddress\\n\\s+\\*\\s+The address' in src/V1/Gapic/SpannerGapicClient.php.
synthtool > Replaced '\\$transportConfig, and any \\$serviceAddress' in src/Admin/Instance/V1/Gapic/InstanceAdminGapicClient.php.
synthtool > Replaced '\\$transportConfig, and any \\$serviceAddress' in src/Admin/Database/V1/Gapic/DatabaseAdminGapicClient.php.
synthtool > Replaced '\\$transportConfig, and any \\$serviceAddress' in src/V1/Gapic/SpannerGapicClient.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/GetInstanceRequest.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/CreateInstanceMetadata.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/ListInstanceConfigsRequest.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/GetInstanceConfigRequest.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/DeleteInstanceRequest.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/UpdateInstanceMetadata.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/UpdateInstanceRequest.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/ListInstancesRequest.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/InstanceConfig.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/ListInstancesResponse.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/CreateInstanceRequest.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/Instance.php.
synthtool > Replaced 'final class' in src/Admin/Instance/V1/ListInstanceConfigsResponse.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/GetDatabaseDdlResponse.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/CreateDatabaseRequest.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/UpdateDatabaseDdlRequest.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/ListDatabasesResponse.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/Database.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/GetDatabaseDdlRequest.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/ListDatabasesRequest.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/DropDatabaseRequest.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/GetDatabaseRequest.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/CreateDatabaseMetadata.php.
synthtool > Replaced 'final class' in src/Admin/Database/V1/UpdateDatabaseDdlMetadata.php.
synthtool > Replaced 'final class' in src/V1/Transaction.php.
synthtool > Replaced 'final class' in src/V1/KeySet.php.
synthtool > Replaced 'final class' in src/V1/KeyRange.php.
synthtool > Replaced 'final class' in src/V1/ResultSetMetadata.php.
synthtool > Replaced 'final class' in src/V1/ResultSetStats.php.
synthtool > Replaced 'final class' in src/V1/DeleteSessionRequest.php.
synthtool > Replaced 'final class' in src/V1/TransactionOptions.php.
synthtool > Replaced 'final class' in src/V1/Type.php.
synthtool > Replaced 'final class' in src/V1/Partition.php.
synthtool > Replaced 'final class' in src/V1/BatchCreateSessionsRequest.php.
synthtool > Replaced 'final class' in src/V1/BatchCreateSessionsResponse.php.
synthtool > Replaced 'final class' in src/V1/CommitResponse.php.
synthtool > Replaced 'final class' in src/V1/ListSessionsRequest.php.
synthtool > Replaced 'final class' in src/V1/CreateSessionRequest.php.
synthtool > Replaced 'final class' in src/V1/PartialResultSet.php.
synthtool > Replaced 'final class' in src/V1/PartitionOptions.php.
synthtool > Replaced 'final class' in src/V1/BeginTransactionRequest.php.
synthtool > Replaced 'final class' in src/V1/PartitionResponse.php.
synthtool > Replaced 'final class' in src/V1/StructType.php.
synthtool > Replaced 'final class' in src/V1/GetSessionRequest.php.
synthtool > Replaced 'final class' in src/V1/PlanNode.php.
synthtool > Replaced 'final class' in src/V1/RollbackRequest.php.
synthtool > Replaced 'final class' in src/V1/ExecuteBatchDmlResponse.php.
synthtool > Replaced 'final class' in src/V1/QueryPlan.php.
synthtool > Replaced 'final class' in src/V1/ExecuteSqlRequest.php.
synthtool > Replaced 'final class' in src/V1/ResultSet.php.
synthtool > Replaced 'final class' in src/V1/Mutation.php.
synthtool > Replaced 'final class' in src/V1/PartitionReadRequest.php.
synthtool > Replaced 'final class' in src/V1/ReadRequest.php.
synthtool > Replaced 'final class' in src/V1/Session.php.
synthtool > Replaced 'final class' in src/V1/ExecuteBatchDmlRequest.php.
synthtool > Replaced 'final class' in src/V1/CommitRequest.php.
synthtool > Replaced 'final class' in src/V1/ListSessionsResponse.php.
synthtool > Replaced 'final class' in src/V1/TransactionSelector.php.
synthtool > Replaced 'final class' in src/V1/PartitionQueryRequest.php.
synthtool > Replaced 'final class' in src/V1/ExecuteBatchDmlRequest/Statement.php.
synthtool > Replaced 'final class' in src/V1/Mutation/Delete.php.
synthtool > Replaced 'final class' in src/V1/Mutation/Write.php.
synthtool > Replaced 'final class' in src/V1/TransactionOptions/ReadWrite.php.
synthtool > Replaced 'final class' in src/V1/TransactionOptions/ReadOnly.php.
synthtool > Replaced 'final class' in src/V1/TransactionOptions/PartitionedDml.php.
synthtool > Replaced 'final class' in src/V1/StructType/Field.php.
synthtool > Replaced 'final class' in src/V1/PlanNode/ShortRepresentation.php.
synthtool > Replaced 'final class' in src/V1/PlanNode/ChildLink.php.
synthtool > No replacements made in ['src/Admin/**/*.php', 'src/V*/**/*.php'] for pattern public function ([s|g]\w{3,})Unwrapped, maybe replacement is not longer needed?
synthtool > Replaced 'Copyright \\d{4}' in src/Admin/Instance/V1/Gapic/InstanceAdminGapicClient.php.
synthtool > Replaced 'Copyright \\d{4}' in src/Admin/Database/V1/Gapic/DatabaseAdminGapicClient.php.
synthtool > Replaced 'Copyright \\d{4}' in src/V1/Gapic/SpannerGapicClient.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/V1/SpannerClientPartialVeneerTest.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/V1/SpannerClientTest.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/Admin/Instance/V1/InstanceAdminClientTest.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/Admin/Database/V1/DatabaseAdminClientTest.php.
synthtool > Replaced 'namespace Google\\\\Cloud\\\\Spanner\\\\Admin\\\\Database\\\\Tests\\\\Unit' in tests/Unit/Admin/Database/V1/DatabaseAdminClientTest.php.
synthtool > Replaced 'namespace Google\\\\Cloud\\\\Spanner\\\\Admin\\\\Instance\\\\Tests\\\\Unit' in tests/Unit/Admin/Instance/V1/InstanceAdminClientTest.php.
synthtool > Replaced '@group database' in tests/Unit/Admin/Database/V1/DatabaseAdminClientTest.php.
synthtool > Replaced '@group instance' in tests/Unit/Admin/Instance/V1/InstanceAdminClientTest.php.
synthtool > Cleaned up 1 temporary directories.
synthtool > Wrote metadata to synth.metadata.

[codecov]

Codecov Report

Merging #2348 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2348   +/-   ##
=========================================
  Coverage     92.49%   92.49%           
  Complexity     4479     4479           
=========================================
  Files           311      311           
  Lines         13358    13358           
=========================================
  Hits          12355    12355           
  Misses         1003     1003

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7e133f1...bf22c65. Read the comment docs.

[jdpedrie]

This is a breaking change. Gapic is marked as @experimental though. Change itself looks fine, but need additional review.