Refs #22634 -- Removed unneeded app_label in custom session engine example.

docs/topics/http/sessions.txt

@@ -800,9 +800,6 @@ to query the database for all active sessions for an account)::
     class CustomSession(AbstractBaseSession):
         account_id = models.IntegerField(null=True, db_index=True)
 
-        class Meta:
-            app_label = 'mysessions'
-
         @classmethod
         def get_session_store_class(cls):
             return SessionStore