Bump pygithub from 2.5.0 to 2.6.1 in /tools/release

Bumps [pygithub](https://github.com/pygithub/pygithub) from 2.5.0 to 2.6.1.
- [Release notes](https://github.com/pygithub/pygithub/releases)
- [Changelog](https://github.com/PyGithub/PyGithub/blob/v2.6.1/doc/changes.rst)
- [Commits](PyGithub/PyGithub@v2.5.0...v2.6.1)

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

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

Author: dependabot[bot]

tools/release/requirements.txt

@@ -1,2 +1,2 @@
-PyGithub==2.5.0
+PyGithub==2.6.1
 pytest==8.3.4