Update Guild.prune_members required permissions notes

Author: fretgfr

discord/guild.py

@@ -2565,7 +2565,7 @@ async def prune_members(
         The inactive members are denoted if they have not logged on in
         ``days`` number of days and they have no roles.
 
-        You must have :attr:`~Permissions.kick_members` to do this.
+        You must have both :attr:`~Permissions.kick_members` and :attr:`~Permissions.manage_guild` to do this.
 
         To check how many members you would prune without actually pruning,
         see the :meth:`estimate_pruned_members` function.