fix annotated assignment (#25094)
Summary:
Fixing parsing for annotated assignment
`List[int] a = []`.
See https://github.com/pytorch/pytorch/pull/24989/files?file-filters%5B%5D=.py for changes to the test_jit_py3 & run_test files.
follow up to https://github.com/pytorch/pytorch/pull/24477 and fix for https://github.com/pytorch/pytorch/issues/25086
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25094
Differential Revision: D16985016
Pulled By: eellison
fbshipit-source-id: 6be1363f2503303b96bd2e6a9f188ad72441f4eb
