Remove unnecessary type ignore

Despite this except branch is no longer guarded, the exceptional
case could still happen if an Object is passed or if a future channel
type leads to breakage

Author: Rapptz

discord/message.py

@@ -1422,7 +1422,7 @@ def __init__(
 
         try:
             # if the channel doesn't have a guild attribute, we handle that
-            self.guild = channel.guild  # type: ignore
+            self.guild = channel.guild
         except AttributeError:
             self.guild = state._get_guild(utils._get_as_snowflake(data, 'guild_id'))