Bump pygit2 from 1.13.0 to 1.13.1 in /services/python

Bumps [pygit2](https://github.com/libgit2/pygit2) from 1.13.0 to 1.13.1.
- [Changelog](https://github.com/libgit2/pygit2/blob/master/CHANGELOG.rst)
- [Commits](libgit2/pygit2@v1.13.0...v1.13.1)

---
updated-dependencies:
- dependency-name: pygit2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

services/python/requirements.txt

@@ -119,7 +119,7 @@ pycodestyle==2.11.0
 pycparser==2.21
 pydot==1.4.2
 pyflakes==3.1.0
-pygit2==1.13.0
+pygit2==1.13.1
 Pygments==2.16.1
 pygtrie==2.5.0
 PyJWT==2.8.0