Update create_dm documentation to say it's a coroutine

discord/user.py

@@ -744,7 +744,9 @@ class User(BaseUser, discord.abc.Messageable):
         return [guild for guild in self._state._guilds.values() if guild.get_member(self.id)]
 
     async def create_dm(self):
-        """Creates a :class:`DMChannel` with this user.
+        """|coro|
+
+        Creates a :class:`DMChannel` with this user.
 
         This should be rarely called, as this is done transparently for most
         people.