[`atomicwrites`](https://github.com/untitaker/python-atomicwrites) is a package that's only really useful for Python 2/3 compatibility. It's now deprecated, archived, and unmaintained. Prior to #8883 a few days ago, marking the stubs as complete, the typeshed stubs hadn't received any significant updates for several years.
I propose we mark the stubs as no longer updated, and then remove them.
* Replace all uses of StrPath, BytesPath, and AnyPath in Python 2 stubs.
* Add StrOrBytesPath as preferred alias for AnyPath.
* Replace all remaining AnyPath instances with StrOrBytesPath.
* Mark AnyPath as obsolete.
Part of #5470
