Add clarifying comment to blacken nox target.

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/redis/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:5fd9aee1d82a00cebf425c8fa431f5457539562f5867ad9c54370f0ec9a7ccaa
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/cloud/redis/artman_redis_v1beta1.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/redis-v1beta1.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/redis/v1beta1/cloud_redis.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/redis-v1beta1/google/cloud/redis_v1beta1/proto/cloud_redis.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/redis-v1beta1/google/cloud/redis_v1beta1/proto.
synthtool > Running generator for google/cloud/redis/artman_redis_v1.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/redis-v1.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/redis/v1/cloud_redis.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/redis-v1/google/cloud/redis_v1/proto/cloud_redis.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/redis-v1/google/cloud/redis_v1/proto.
synthtool > No replacements made in google/cloud/**/cloud_redis_client.py for pattern resources of the form:\n      ``, maybe replacement is not longer needed?
synthtool > No replacements made in google/cloud/**/cloud_redis_client.py for pattern 
            parent \(str\): Required. The resource name of the instance location using the form:
                ::

                    `projects/{project_id}/locations/{location_id}`
                where ``location_id`` refers to a GCP region, maybe replacement is not longer needed?
synthtool > No replacements made in google/cloud/**/cloud_redis_client.py for pattern 
                with the following restrictions:

                \* Must contain only lowercase letters, numbers, and hyphens\., maybe replacement is not longer needed?
synthtool > No replacements made in google/cloud/**/cloud_redis_client.py for pattern 
            name \(str\): Required. Redis instance resource name using the form:
                ::

                    `projects/{project_id}/locations/{location_id}/instances/{instance_id}`
                where ``location_id`` refers to a GCP region, maybe replacement is not longer needed?
synthtool > No replacements made in google/cloud/**/cloud_redis_client.py for pattern 
                fields from ``Instance``:

                 \*   ``displayName``
                 \*   ``labels``
                 \*   ``memorySizeGb``
                 \*   ``redisConfig``, maybe replacement is not longer needed?
.coveragerc
.flake8
MANIFEST.in
noxfile.py.j2
setup.cfg
Running session blacken
Creating virtualenv using python3.6 in /tmpfs/src/git/autosynth/working_repo/redis/.nox/blacken
pip install --upgrade black
black google tests docs
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/__init__.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/__init__.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1/__init__.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1/gapic/transports/cloud_redis_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1/gapic/cloud_redis_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1/types.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1beta1/__init__.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1/proto/cloud_redis_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1beta1/gapic/cloud_redis_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1beta1/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1/gapic/cloud_redis_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1beta1/gapic/transports/cloud_redis_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1beta1/proto/cloud_redis_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1beta1/types.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1beta1/gapic/cloud_redis_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/tests/unit/gapic/v1/test_cloud_redis_client_v1.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/tests/unit/gapic/v1beta1/test_cloud_redis_client_v1beta1.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1beta1/proto/cloud_redis_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/redis/google/cloud/redis_v1/proto/cloud_redis_pb2.py
All done! ✨ 🍰 ✨
21 files reformatted, 7 files left unchanged.
Session blacken was successful.
synthtool > Cleaned up 2 temporary directories.
synthtool > Wrote metadata to synth.metadata.