build(deps-dev): bump @octokit/rest from 20.1.1 to 21.0.0

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 20.1.1 to 21.0.0.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](octokit/rest.js@v20.1.1...v21.0.0)

---
updated-dependencies:
- dependency-name: "@octokit/rest"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -15,7 +15,7 @@
     "probot": "^13.3.0"
   },
   "devDependencies": {
-    "@octokit/rest": "^20.1.1",
+    "@octokit/rest": "^21.0.0",
     "@vercel/node": "^3.1.7",
     "fetch-mock": "^10.0.5",
     "prettier": "^3.3.2",