Mark django max version (#42)

requirements/base.txt

@@ -12,7 +12,7 @@ unidiff==0.7.5  # https://github.com/matiasb/python-unidiff
 
 # Django
 # ------------------------------------------------------------------------------
-django==4.2.9  # https://www.djangoproject.com/
+django==4.2.9  # pyup: < 5.0 # https://www.djangoproject.com/
 django-environ==0.11.2  # https://github.com/joke2k/django-environ
 django-model-utils==4.3.1  # https://github.com/jazzband/django-model-utils
 django-allauth==0.60.0  # https://github.com/pennersr/django-allauth