IsAdmin permissions changed to IsAdminUser (encode#8227)

Documentation change to keep up with the code permission changes.

Co-authored-by: Jeremy Langley <[email protected]>

Author: Back2Basics

docs/api-guide/viewsets.md

@@ -125,7 +125,7 @@ You may inspect these attributes to adjust behaviour based on the current action
         if self.action == 'list':
             permission_classes = [IsAuthenticated]
         else:
-            permission_classes = [IsAdmin]
+            permission_classes = [IsAdminUser]
         return [permission() for permission in permission_classes]
 
 ## Marking extra actions for routing

docs/community/3.9-announcement.md

@@ -110,7 +110,7 @@ You can now compose permission classes using the and/or operators, `&` and `|`.
 For example...
 
 ```python
-permission_classes = [IsAuthenticated & (ReadOnly | IsAdmin)]
+permission_classes = [IsAuthenticated & (ReadOnly | IsAdminUser)]
 ```
 
 If you're using custom permission classes then make sure that you are subclassing