Logging: Re-add "generated" markers (via synth).

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/logging/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:45263333b058a4b3c26a8b7680a2710f43eae3d250f791a6cb66423991dcb2df
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/logging/artman_logging.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/logging-v2.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/logging/v2/logging.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/logging-v2/google/cloud/logging_v2/proto/logging.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/logging/v2/logging_config.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/logging-v2/google/cloud/logging_v2/proto/logging_config.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/logging/v2/log_entry.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/logging-v2/google/cloud/logging_v2/proto/log_entry.proto
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/logging/v2/logging_metrics.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/logging-v2/google/cloud/logging_v2/proto/logging_metrics.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/logging-v2/google/cloud/logging_v2/proto.
synthtool > Replaced '(^.*$\\n)*' in google/cloud/logging_v2/proto/logging_config_pb2.py.
synthtool > Replaced '(^.*$\\n)*' in google/cloud/logging_v2/proto/logging_metrics_pb2.py.
synthtool > Replaced '(^.*$\\n)*' in google/cloud/logging_v2/proto/log_entry_pb2.py.
synthtool > Replaced '(^.*$\\n)*' in google/cloud/logging_v2/proto/logging_pb2.py.
.coveragerc
.flake8
MANIFEST.in
noxfile.py.j2
setup.cfg
Running session blacken
Creating virtualenv using python3.6 in .nox/blacken
pip install black
black google tests docs
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/config_service_v2_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/logging_service_v2_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/metrics_service_v2_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/transports/config_service_v2_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/transports/logging_service_v2_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/transports/metrics_service_v2_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/metrics_service_v2_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/proto/log_entry_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/logging_service_v2_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/gapic/config_service_v2_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/proto/logging_config_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/proto/logging_metrics_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/proto/log_entry_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/proto/logging_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/proto/logging_metrics_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/tests/unit/gapic/v2/test_logging_service_v2_client_v2.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/proto/logging_config_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/google/cloud/logging_v2/proto/logging_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/tests/unit/gapic/v2/test_config_service_v2_client_v2.py
reformatted /tmpfs/src/git/autosynth/working_repo/logging/tests/unit/gapic/v2/test_metrics_service_v2_client_v2.py
All done! ✨ 🍰 ✨
21 files reformatted, 52 files left unchanged.
Session blacken was successful.
synthtool > Cleaned up 2 temporary directories.
synthtool > Wrote metadata to synth.metadata.