Remove Pinned MinDependency on cryptography

[scbedd]

Essentially, this PR was committed to enable a release.

Longer term, we definitely want to test the earlier version of crypto, but until we remove PyJWT, we won't be able to do that.

Description from @chlowell

In a nutshell, we have azure-identity -> cryptography and azure-identity -> msal -> PyJWT -> cryptography. Min cryptography is 2.1.4 for azure-identity but the latest PyJWT requires 3.3+ and will raise given < 3.2. So, mindependency can't pass. I think msal should drop PyJWT but in the meantime I need to pass mindependency. I could just raise azure-identity's min cryptography, that's ugly but I guess workable for a beta release

[scbedd]

Charles did offline investigation on this, and discovered that the new pip resolver will do the right thing.

pip install msal==1.12.0 cryptography==2.1.4

pip 21.1.1
cryptography 2.1.4
msal 1.12.0
PyJWT 1.7.1

But 20.2 does not, at least on 3 (works on 2.7):

pip 20.2
cryptography 2.1.4
msal 1.12.0
PyJWT 2.1.0

So what we need to do is A) upgrade pip to 20.3, as that is the newest version that has the new resolver + still supports py27 and B) verify that the transitive deps install the way we want. Will be filing a draft PR to test this.