fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-DJANGO-7886958
- https://snyk.io/vuln/SNYK-PYTHON-DJANGO-7886959

requirements.txt

@@ -2,7 +2,7 @@ asgiref==3.7.2
 certifi==2023.7.22
 charset-normalizer==3.1.0
 crispy-bootstrap5==0.7
-Django==4.2.3
+Django==4.2.16
 django-crispy-forms==2.0
 idna==3.4
 pandoc==2.3