[issue46386] Improve `test_typing::test_immutability_by_copy_and_pickle`

[Alex Waygood]

Change by Alex Waygood <Alex.Waygood at Gmail.com>:


----------
nosy: +gvanrossum, kj

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue46386>
_______________________________________