Refs #35844 -- Used asgiref.sync.iscoroutinefunction() instead of deprecated asyncio.iscoroutinefunction().

Fixes DeprecationWarning:

'asyncio.iscoroutinefunction' is deprecated and slated for removal in
Python 3.16; use inspect.iscoroutinefunction() instead.

tests/auth_tests/test_decorators.py

@@ -1,4 +1,4 @@
-from asyncio import iscoroutinefunction
+from asgiref.sync import iscoroutinefunction
 
 from django.conf import settings
 from django.contrib.auth import models