chore(all): auto-regenerate .pb.go files (googleapis#879)

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.

There is no corresponding google-cloud-go PR.

Changes:

chore: use gapic-generator-python 1.2.0
  PiperOrigin-RevId: 467286830
  Source-Link: googleapis/googleapis@e6e875a

chore: regenerate API index

  Source-Link: googleapis/googleapis@ee4650b

feat: Created client libraries for Maps Platform Datasets API
  PiperOrigin-RevId: 467266924
  Source-Link: googleapis/googleapis@0e4fd8a