bpo-46546: remove method_name var leak from importlib.DeprecatedList

[sobolevn]

Related #30955

https://bugs.python.org/issue46546

[AlexWaygood]

Unrelated to this specific PR, but related to the problem in general: there's a small list of global-variable name leaks here that you might be interested in ;)

I think the inspect entries on that list have already been fixed by the addition of __all__ in #30003 on the main branch, but explicitly del-ing those names from globals might be a good idea for 3.10 and 3.9, given that it's essentially a bug that these names are exposed, and those branches accept bugfixes.

[sobolevn]

Thanks! I was using astpath './/For/parent::body/parent::ClassDef' to inspect classes with for in bodies, I think I can easily adapt it to use Module as well!

[sobolevn]

Replaced by python/importlib_metadata#365