Bump Django to 4.2.20

Author: swrichards

requirements/base.txt

@@ -91,7 +91,7 @@ defusedxml==0.7.1
     # via odfpy
 diff-match-patch==20200713
     # via django-import-export
-django==4.2.18
+django==4.2.20
     # via
     #   -r requirements/base.in
     #   django-admin-index

requirements/ci.txt

@@ -181,7 +181,7 @@ diff-match-patch==20200713
     #   django-import-export
 dill==0.3.7
     # via pylint
-django==4.2.18
+django==4.2.20
     # via
     #   -c requirements/base.txt
     #   -r requirements/base.txt

requirements/dev.txt

@@ -219,7 +219,7 @@ dill==0.3.7
     #   -c requirements/ci.txt
     #   -r requirements/ci.txt
     #   pylint
-django==4.2.18
+django==4.2.20
     # via
     #   -c requirements/ci.txt
     #   -r requirements/ci.txt