chore(all): auto-regenerate gapics (#5663)

This is an auto-generated regeneration of the gapic clients by
cloud.google.com/go/internal/gapicgen. Once the corresponding genproto PR is
submitted, genbot will update this PR with a newer dependency to the newer
version of genproto and assign reviewers to this PR.

If you have been assigned to review this PR, please:

- Ensure that the version of genproto in go.mod has been updated.
- Ensure that CI is passing. If it's failing, it requires your manual attention.
- Approve and submit this PR if you believe it's ready to ship.

Corresponding genproto PR: googleapis/go-genproto#761

Changes:

feat(orgpolicy): Deprecates AlternativePolicySpec
  PiperOrigin-RevId: 428897918
  Source-Link: googleapis/googleapis@bbb3c1f

fix(channel): clarify language
  PiperOrigin-RevId: 428802866
  Source-Link: googleapis/googleapis@8cb4699

feat(documentai): add `symbols` field, and auto-format comments
  PiperOrigin-RevId: 428800506
  Source-Link: googleapis/googleapis@ea20380

feat(documentai): add `symbols` field, and auto-format comments
  PiperOrigin-RevId: 428799963
  Source-Link: googleapis/googleapis@8b6181f