pycrypto is unmaintained and vulnerable: pycrypto/pycrypto#285

My CI builder fails it's security scan every month because of this single requirement in ansible.posix unit tests.

Found in code here: https://github.com/ansible-collections/ansible.posix/blame/cdb442ea4890558b75aa3b2bd8c4165455cfc44f/tests/unit/requirements.txt#L3

I am aware I could make an exclusion, but why not fix the issue at the source? (here I mean)