fix: bump release-please from 13.20.0 to 13.21.0 (#559)

Bumps [release-please](https://github.com/googleapis/release-please) from 13.20.0 to 13.21.0.
- [Release notes](https://github.com/googleapis/release-please/releases)
- [Changelog](https://github.com/googleapis/release-please/blob/main/CHANGELOG.md)
- [Commits](https://github.com/googleapis/release-please/compare/v13.20.0...v13.21.0)

---
updated-dependencies:
- dependency-name: release-please
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -26,7 +26,7 @@
   "homepage": "https://github.com/bcoe/release-please-action#readme",
   "dependencies": {
     "@actions/core": "^1.6.0",
-    "release-please": "^13.20.0"
+    "release-please": "^13.21.0"
   },
   "devDependencies": {
     "@vercel/ncc": "^0.27.0",