Update pyproject.toml to bump cryptography version minimum

[pixitha]

Bumping cryptography to 42 minimum, when they added the not_valid_before_utc function to the cryptography library.

not_valid_before_utc

Added in version 42.0.0.

Was getting an error when it was using version 41.0.7 on my machine.

[fulder]

Thank you for your contribution @pixitha, you're right it should be bumped to 42.0.0 as the minimum version. Just don't forget to update the poetry.lock file as well.