[3.12] remove type annotations from multiprocessing. (GH-129381) (#129471)

remove type annotations from multiprocessing. (GH-129381)

* remove type annotations from multiprocessing.

One of them was technically invalid per typing specs... but since we're not
checking these in the stdlib today lets elide them.

https://discuss.python.org/t/static-type-annotations-in-cpython/65068/13

* use the actual comment style annotation format



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(cherry picked from commit 71aecc284efdf997939568a4167dbffe1a65b9bf)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
Co-authored-by: 🇺🇦 Sviatoslav Sydorenko (Святослав Сидоренко) <wk.cvs.github@sydorenko.org.ua>