[docs] Update notes for get_user and get_member

Author: pikaninja

discord/client.py

@@ -1362,7 +1362,7 @@ async def fetch_user(self, user_id):
 
         .. note::
 
-            This method is an API call. For general usage, consider :meth:`get_user` instead.
+            This method is an API call. If you have :attr:`Intents.members` and member cache enabled, consider :meth:`get_user` instead.
 
         Parameters
         -----------

discord/guild.py

@@ -1375,7 +1375,7 @@ async def fetch_member(self, member_id):
 
         .. note::
 
-            This method is an API call. For general usage, consider :meth:`get_member` instead.
+            This method is an API call. If you have :attr:`Intents.members` and member cache enabled, consider :meth:`get_member` instead.
 
         Parameters
         -----------