tests: Test with Django 5.1 RC (#3370)

Author: sentrivana

tox.ini

@@ -396,7 +396,7 @@ deps =
     django-v4.1: Django~=4.1.0
     django-v4.2: Django~=4.2.0
     django-v5.0: Django~=5.0.0
-    django-v5.1: Django==5.1b1
+    django-v5.1: Django==5.1rc1
     django-latest: Django
 
     # Falcon