chore(all): auto-regenerate .pb.go files (googleapis#608)

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#4193

Changes:

chore: regenerate API index

  Source-Link: googleapis/googleapis@0b26f05

fix!: Specify namespace options for C# and PHP.
  This is only a breaking change for C# and PHP, which haven't published client libraries for this API yet.

  PiperOrigin-RevId: 376845575
  Source-Link: googleapis/googleapis@5908eff

regen.txt

@@ -1 +1 @@
-1c20dcfd8052a2bea026bda36875e5b7606028db
+0b26f05c9f469dc710e13a94f10d46dae4fa0b3c