Merged release PRs create no release under REST API version 2026-03-10

Environment details

• OS: ubuntu-latest GitHub Actions runner
• Node.js version: 24, through googleapis/[email protected]
• npm version: none, release-please runs inside the action
• release-please version: 17.11.2

Steps to reproduce

1. Read a merged release PR with REST API version 2026-03-10. gh api -H 'X-GitHub-Api-Version: 2026-03-10' repos/googleapis/release-please/pulls/2888 returns no merge_commit_sha, and 2022-11-28 returns 05c6a4f71022304d4edad24ea90c1c16324503d5. GitHub removed the field in that version: https://docs.github.com/en/rest/about-the-rest-api/breaking-changes?apiVersion=2026-03-10
2. release-please lists merged release PRs over REST and takes their sha from merge_commit_sha: https://github.com/googleapis/release-please/blob/v17.11.2/src/manifest.ts#L1146-L1153 https://github.com/googleapis/release-please/blob/v17.11.2/src/github-api.ts#L405
3. Without a sha, buildRelease logs Pull request should have been merged and creates no tag or release, and the run still ends green: https://github.com/googleapis/release-please/blob/v17.11.2/src/strategies/base.ts#L602-L605