fix: cvat/requirements/base.txt to reduce vulnerabilities (#4369)

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-GITPYTHON-2407255

cvat/requirements/base.txt

@@ -22,7 +22,7 @@ django-sendfile2==0.6.1
 dj-pagination==2.5.0
 python-logstash-async==2.2.0
 rules==2.2
-GitPython==3.1.8
+GitPython==3.1.27
 coreapi==2.3.3
 django-filter==2.4.0
 Markdown==3.2.2