Drop cryptography dependencies check

[jas4711]

No description provided.

[jas4711]

I noticed this problem independently of #83 but I agree with @cjwatson that the cryptography version check is probably unnecessary, so aligning this merge request with that

[dainnilsson]

Thanks for pointing out the issue, we are overdue for a new release of the library,even if it is just a dependency version bump. That said, the upper bound is in place to ensure compatibility and we do take care to test the latest supported version when we make a new release. Cryptography uses a versioning scheme where if a feature exists and does not emit a deprecation warning in version X, it is guaranteed to still be available in X+2. Thus, if we test and ensure compatibility (and no usage of deprecated functions) with version Y, we will set the requirement to be < Y+3.

Given that the latest version of cryptography is currently 49, we need to fully test this version and then bump the requirement to <52. That, and create a new release.