Fix annotation for ast.alias.name

[AlexWaygood]

This isn't necessarily always an identifier:

>>> print(ast.dump(ast.parse('from typing import *'), indent=2))
Module(
  body=[
    ImportFrom(
      module='typing',
      names=[
        alias(name='*')],
      level=0)],
  type_ignores=[])
>>> '*'.isidentifier()
False

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉