Update dependency django_csp to v4

requirements.txt

@@ -11,7 +11,7 @@ django-simple-history==3.8.0
 django-split-settings==1.3.2
 django-tex==1.1.10
 django-timezone-field==7.1
-django_csp==3.8
+django_csp==4.0
 djangorestframework==3.16.0
 
 fontawesomefree==6.6.0  # Makes static files (css, fonts) available locally