Bug 1949905 [wpt PR 50888] - Bump pygithub from 2.5.0 to 2.6.1 in /tools, a=testonly

Automatic update from web-platform-tests
Bump pygithub from 2.5.0 to 2.6.1 in /tools

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] <supportgithub.com>
--

wpt-commits: 87d35f560e994323f621b23a2970c33c30209c0a
wpt-pr: 50888

UltraBlame original commit: 65982afc606c7f39fb5185dbb9df15e7fe71cc2c

Author: marco-c

testing/web-platform/tests/tools/ci/requirements_tc.txt

@@ -3,9 +3,9 @@ pygithub
 =
 2
 .
-5
+6
 .
-0
+1
 pyyaml
 =
 =