chore(python): bump pygithub in /docs in the documentation group

Bumps the documentation group in /docs with 1 update: [pygithub](https://github.com/pygithub/pygithub).


Updates `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
  dependency-group: documentation
...

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

docs/source/requirements.txt

@@ -14,4 +14,4 @@ mkdocs-macros-plugin==1.3.7
 mkdocs-redirects==1.2.1
 material-plausible-plugin==0.2.0
 markdown-exec[ansi]==1.10.0
-pygithub==2.5.0
+pygithub==2.6.1