docs: Update documentation.

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/VideoIntelligence/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:ef1a98ab1e2b8f05f4d9a56f27d63347aefe14020e5f2d585172b14ca76f1d90
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/cloud/videointelligence/artman_videointelligence_v1.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/php/google-cloud-video-intelligence-v1.
synthtool > Running generator for google/cloud/videointelligence/artman_videointelligence_v1beta2.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/php/google-cloud-video-intelligence-v1beta2.
synthtool > Replaced 'Copyright \\d{4}' in src/V1/Gapic/VideoIntelligenceServiceGapicClient.php.
synthtool > Replaced 'Copyright \\d{4}' in src/V1beta2/Gapic/VideoIntelligenceServiceGapicClient.php.
synthtool > Replaced 'Copyright \\d{4}' in src/V1/VideoIntelligenceServiceClient.php.
synthtool > Replaced 'Copyright \\d{4}' in src/V1beta2/VideoIntelligenceServiceClient.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/V1/VideoIntelligenceServiceClientTest.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/V1beta2/VideoIntelligenceServiceClientTest.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/System/V1/VideoIntelligenceServiceClientTest.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/System/V1/VideoIntelligenceServiceSmokeTest.php.
synthtool > Replaced '^(\\s+\\*\\n)?\\s+\\*\\s@experimental\\n' in src/V1/VideoIntelligenceServiceClient.php.
synthtool > Replaced '^(\\s+\\*\\n)?\\s+\\*\\s@experimental\\n' in src/V1/Gapic/VideoIntelligenceServiceGapicClient.php.
synthtool > Cleaned up 1 temporary directories.
synthtool > Wrote metadata to synth.metadata.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@0fc4c0b). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2043   +/-   ##
=========================================
  Coverage          ?   92.57%           
  Complexity        ?     4378           
=========================================
  Files             ?      304           
  Lines             ?    13012           
  Branches          ?        0           
=========================================
  Hits              ?    12046           
  Misses            ?      966           
  Partials          ?        0

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