Bump pygithub from 1.55 to 1.56 in /tools

Bumps [pygithub](https://github.com/pygithub/pygithub) from 1.55 to 1.56.
- [Release notes](https://github.com/pygithub/pygithub/releases)
- [Changelog](https://github.com/PyGithub/PyGithub/blob/master/doc/changes.rst)
- [Commits](PyGithub/PyGithub@v1.55...v1.56)

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

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

tools/ci/requirements_tc.txt

@@ -1,4 +1,4 @@
-pygithub==1.55
+pygithub==1.56
 pyyaml==6.0
 requests==2.27.1
 taskcluster==44.22.0