Text to Speech: Allow kwargs to be passed to create_channel (via synth).

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/texttospeech/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:b036a7f4278d9deb5796f065e5c7f608d47d75369985ca7ab5039998120e972d
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/cloud/texttospeech/artman_texttospeech_v1beta1.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/texttospeech-v1beta1.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/texttospeech/v1beta1/cloud_tts.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/texttospeech-v1beta1/google/cloud/texttospeech_v1beta1/proto/cloud_tts.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/texttospeech-v1beta1/google/cloud/texttospeech_v1beta1/proto.
synthtool > Running generator for google/cloud/texttospeech/artman_texttospeech_v1.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/texttospeech-v1.
synthtool > Copy: /home/kbuilder/.cache/synthtool/googleapis/google/cloud/texttospeech/v1/cloud_tts.proto to /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/texttospeech-v1/google/cloud/texttospeech_v1/proto/cloud_tts.proto
synthtool > Placed proto files into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/texttospeech-v1/google/cloud/texttospeech_v1/proto.
synthtool > No replacements made in **/gapic/*_client.py for pattern \\"(.+?)-\*\\", maybe replacement is not longer needed?
.coveragerc
.flake8
MANIFEST.in
noxfile.py.j2
setup.cfg
Running session blacken
Creating virtualenv using python3.6 in .nox/blacken
pip install black
black docs google tests noxfile.py setup.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1/__init__.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1/gapic/text_to_speech_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1/gapic/transports/text_to_speech_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1/types.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1/proto/cloud_tts_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1beta1/__init__.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1beta1/gapic/enums.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1/gapic/text_to_speech_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1beta1/gapic/text_to_speech_client_config.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1beta1/gapic/transports/text_to_speech_grpc_transport.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1beta1/gapic/text_to_speech_client.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1beta1/proto/cloud_tts_pb2_grpc.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1beta1/types.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/tests/unit/gapic/v1/test_text_to_speech_client_v1.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/noxfile.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/tests/unit/gapic/v1beta1/test_text_to_speech_client_v1beta1.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1beta1/proto/cloud_tts_pb2.py
reformatted /tmpfs/src/git/autosynth/working_repo/texttospeech/google/cloud/texttospeech_v1/proto/cloud_tts_pb2.py
All done! ✨ 🍰 ✨
20 files reformatted, 10 files left unchanged.
Session blacken was successful.
synthtool > Cleaned up 2 temporary directories.
synthtool > Wrote metadata to synth.metadata.