Bump discord.py to 1.7.0 (#4928)

* Bump discord.py, but to the git version for now

* Import GuildConverter from d.py and deprecate our implementation

* Import PartialMessageConverter in our commands extension

* Use newly added `Cog.has_error_handler()` rather than private method

* Update snowflake regex to use 20 as max length

See Rapptz/discord.py#6501

* Use new supported way for custom cooldown buckets

* Include group args in command signature

* Update code to use `Client.close()` over `Client.logout()`

* Add StageChannelConverter and StoreChannelConverter

* Fix AttributeError in licenseinfo

redbot/core/commands/requires.py

@@ -28,7 +28,6 @@ from typing import (
 import discord
 
 from discord.ext.commands import check
-from .converter import GuildConverter
 from .errors import BotMissingPermissions
 
 if TYPE_CHECKING:
@@ -70,7 +69,7 @@ GlobalPermissionModel = Union[
     discord.TextChannel,
     discord.CategoryChannel,
     discord.Role,
-    GuildConverter,  # Unfortunately this will have to do for now
+    discord.Guild,
 ]
 GuildPermissionModel = Union[
     discord.Member,
@@ -78,7 +77,7 @@ GuildPermissionModel = Union[
     discord.TextChannel,
     discord.CategoryChannel,
     discord.Role,
-    GuildConverter,
+    discord.Guild,
 ]
 PermissionModel = Union[GlobalPermissionModel, GuildPermissionModel]
 CheckPredicate = Callable[["Context"], Union[Optional[bool], Awaitable[Optional[bool]]]]