Bump gitpython from 3.1.13 to 3.1.15

Bumps [gitpython](https://github.com/gitpython-developers/GitPython) from 3.1.13 to 3.1.15.
- [Release notes](https://github.com/gitpython-developers/GitPython/releases)
- [Changelog](https://github.com/gitpython-developers/GitPython/blob/main/CHANGES)
- [Commits](gitpython-developers/GitPython@3.1.13...3.1.15)

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

Author: dependabot[bot]

requirements/base.txt

@@ -45,4 +45,4 @@ PyYAML==5.4.1
 osmcha==0.8.2
 
 # git python is required by the frontend management command
-GitPython==3.1.13
+GitPython==3.1.15