Remove unused ConversionFailure (#6113)

redbot/core/commands/errors.py

@@ -4,23 +4,12 @@ import discord
 from discord.ext import commands
 
 __all__ = (
-    "ConversionFailure",
     "BotMissingPermissions",
     "UserFeedbackCheckFailure",
     "ArgParserFailure",
 )
 
 
-class ConversionFailure(commands.BadArgument):
-    """Raised when converting an argument fails."""
-
-    def __init__(self, converter, argument: str, param: inspect.Parameter, *args):
-        self.converter = converter
-        self.argument = argument
-        self.param = param
-        super().__init__(*args)
-
-
 class BotMissingPermissions(commands.CheckFailure):
     """Raised if the bot is missing permissions required to run a command."""