chore(all): auto-regenerate gapics (#3661)

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#526

Changes:

feat(channel): Add Pub/Sub endpoints for Cloud Channel API.
  PiperOrigin-RevId: 355059873
  Source-Link: googleapis/googleapis@6ef9eae

Author: yoshi-automation