potential release issue: docs warning

The [latest release PR](https://github.com/googleapis/google-cloud-python/pull/15477) is mergable but it has a failed check: [docs / Docs warnings: will block release (pull_request)](https://github.com/googleapis/google-cloud-python/actions/runs/21240756240/job/61117944025?pr=15477).

I merged the PR, but I just wanted to call out in case this is an issue.

