Discord.py dep update 3.1 (#2587)

* Dependency update

discord.py==1.0.1
websockets<7

[style]
black==19.3b0

[Docs]
jinja==2.10.1
urllib3==1.24.2

Changes related to breaking changes from discord.py have also been made
to match

As of this commit, help formatter is back to discord.py's default

redbot/cogs/audio/audio.py

@@ -3493,6 +3493,7 @@ class Audio(commands.Cog):
         )
         return r
 
+    @commands.Cog.listener()
     async def on_voice_state_update(self, member, before, after):
         if after.channel != before.channel:
             try:
@@ -3500,7 +3501,7 @@ class Audio(commands.Cog):
             except (ValueError, KeyError, AttributeError):
                 pass
 
-    def __unload(self):
+    def cog_unload(self):
         if not self._cleaned_up:
             self.session.detach()
 
@@ -3515,8 +3516,9 @@ class Audio(commands.Cog):
             shutdown_lavalink_server()
             self._cleaned_up = True
 
-    __del__ = __unload
+    __del__ = cog_unload
 
+    @commands.Cog.listener()
     async def on_guild_remove(self, guild: discord.Guild):
         """
         This is to clean up players when