Speech: 'result_end_time', docstring changes via synth.

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Cloning googleapis.
synthtool > Running generator for google/cloud/speech/artman_speech_v1p1beta1.yaml.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:229601142daed005bf56fbaa21a02cf7aa0b261b57677d38306f8013e536de7a
Status: Image is up to date for googleapis/artman:latest
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/speech-v1p1beta1.
synthtool > Running generator for google/cloud/speech/artman_speech_v1.yaml.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:229601142daed005bf56fbaa21a02cf7aa0b261b57677d38306f8013e536de7a
Status: Image is up to date for googleapis/artman:latest
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/python/speech-v1.
synthtool > Replaced '(^.*$\\n)*' in google/cloud/speech_v1p1beta1/proto/cloud_speech_pb2.py.
synthtool > Replaced '(^.*$\\n)*' in google/cloud/speech_v1/proto/cloud_speech_pb2.py.
synthtool > Replaced 'from google\\.cloud import speech_(.+?)$' in tests/unit/gapic/v1/test_speech_client_v1.py.
synthtool > Replaced 'from google\\.cloud import speech_(.+?)$' in tests/unit/gapic/v1p1beta1/test_speech_client_v1p1beta1.py.
synthtool > Cleaned up 0 temporary directories.

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