chore(all): auto-regenerate .pb.go files (#668)

This is an auto-generated regeneration of the .pb.go files by
cloud.google.com/go/internal/gapicgen. Once this PR is submitted, genbot will
update the corresponding PR to depend on the newer version of go-genproto, and
assign reviewers. Whilst this or any regen PR is open in go-genproto, genbot
will not create any more regeneration PRs. If all regen PRs are closed,
gapicgen will create a new set of regeneration PRs once per night.

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

- 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. That will prompt
genbot to assign reviewers to the google-cloud-go PR.

Corresponding google-cloud-go PR: googleapis/google-cloud-go#4701

Changes:

chore: regenerate API index

  Source-Link: googleapis/googleapis@298a980

feat: Add `OnPremCluster` and `MultiCloudCluster` as `GkeCluster` equivalent field
  feat!: Move `GkeCluster` under oneof

  PiperOrigin-RevId: 393865355
  Source-Link: googleapis/googleapis@fbae10c

chore: regenerate API index

  Source-Link: googleapis/googleapis@2e9e9ef

feat(aiplatform): add XAI, model monitoring, and index services to aiplatform v1
  Committer: @dizcology
  PiperOrigin-RevId: 393860361
  Source-Link: googleapis/googleapis@8031cc2

chore: regenerate API index

  Source-Link: googleapis/googleapis@583dd6a

feat: added support for Notebooks v1
  Committer: @gogasca
  PiperOrigin-RevId: 393792683
  Source-Link: googleapis/googleapis@03ce2eb

chore(bazel): update rules_gapic to v0.6.2
  PiperOrigin-RevId: 393792439
  Source-Link: googleapis/googleapis@c1296cd