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/image/image.py

@@ -24,7 +24,7 @@ class Image(commands.Cog):
         self.session = aiohttp.ClientSession()
         self.imgur_base_url = "https://api.imgur.com/3/"
 
-    def __unload(self):
+    def cog_unload(self):
         self.session.detach()
 
     async def initialize(self) -> None: