chore: update go-mockgen

[efritz]

go-mockgen v1.1.3 has the incorrect version string, meaning that it re-downloaded go-mockgen on every go-generate command. This bumps the version so that we have a stable version string.

Should improve build times.

Test plan

Affects the build, not the product.

[sourcegraph-bot]

Codenotify: Notifying subscribers in CODENOTIFY files for diff 33f09a6...efb3f32.

Notify	File(s)
@beyang	enterprise/cmd/precise-code-intel-worker/internal/worker/mock_iface_test.go enterprise/cmd/precise-code-intel-worker/internal/worker/mock_worker_store_test.go internal/search/job/job_mock_test.go
@bobheadxi	docker-images/prometheus/cmd/prom-wrapper/mocks/prometheus_mock.go
@camdencheek	internal/search/job/job_mock_test.go
@eseliger	enterprise/cmd/frontend/internal/executorqueue/handler/mock_iface_test.go enterprise/cmd/frontend/internal/executorqueue/queues/batches/mock_iface_test.go enterprise/internal/batches/reconciler/mock_changeset_source_test.go enterprise/internal/batches/syncer/mock_iface_test.go
@indradhanush	cmd/gitserver/server/mock_iface_test.go internal/gitserver/mock_client.go
@keegancsmith	cmd/symbols/internal/api/mock_iface_test.go cmd/symbols/internal/fetcher/mock_iface_test.go internal/search/job/job_mock_test.go
@ryanslade	cmd/gitserver/server/mock_iface_test.go internal/gitserver/mock_client.go
@sourcegraph/code-insights-backend	enterprise/internal/insights/background/mock_repo_store.go enterprise/internal/insights/compression/mock_commit_store.go enterprise/internal/insights/discovery/mock_indexable_repos_lister.go enterprise/internal/insights/discovery/mock_repo_store.go enterprise/internal/insights/discovery/mock_setting_store.go enterprise/internal/insights/store/mock_store_dataseriesstore.go enterprise/internal/insights/store/mock_store_insightmetadatastore.go enterprise/internal/insights/store/mock_store_interface.go
@unknwon	internal/authz/mock_sub_repo_perms_checker.go internal/authz/mock_sub_repo_perms_getter.go