fix: requirements/base.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/base.txt

@@ -10,7 +10,7 @@ psycopg2-binary==2.9.5 # https://github.com/psycopg/psycopg2-wheels
 
 # Django
 # ------------------------------------------------------------------------------
-django==4.1.3  # pyup: < 3.1  # https://www.djangoproject.com/
+django==4.2.16  # pyup: < 3.1  # https://www.djangoproject.com/
 django-environ==0.9.0  # https://github.com/joke2k/django-environ
 django-model-utils==4.3.1  # https://github.com/jazzband/django-model-utils
 django-allauth==0.51.0  # https://github.com/pennersr/django-allauth