Merge branch 'bump-gitpython' into 'master'

Bump Python requirement gitpython to 3.1.18

See merge request !1378

requirements.txt

@@ -11,7 +11,7 @@ django-rq==2.4.1
 djangorestframework==3.12.4
 drf-spectacular==0.17.2
 elasticsearch-dsl>=6.0.0,<7.0.0
-gitpython==3.1.17
+gitpython==3.1.18
 python-gitlab==2.8.0
 python-memcached==1.59
 pytz==2021.1