[commands] Disallow float/complex in Literal but allow None

Type checkers (both mypy and pydantic) apparently don't like it

discord/ext/commands/core.py

@@ -136,7 +136,7 @@ def _evaluate_annotation(
             _evaluate_annotation(arg, globals, locals, cache, implicit_str=implicit_str) for arg in args
         )
 
-        if is_literal and not all(isinstance(x, (str, int, bool, float, complex)) for x in evaluated_args):
+        if is_literal and not all(isinstance(x, (str, int, bool, type(None))) for x in evaluated_args):
             raise TypeError('Literal arguments must be of type str, int, bool, float or complex.')
 
         if evaluated_args == args: