Roll back crypto library version

This is a temporary reversion to 3.3.2 for the cryptography library.
There's an issue with buildx failing for the arm/v7 build, which is
directly related to cryptography versions > 3.3.2 (after the switch to
rust).

It might be acceptable to include the rust toolchain for armv7 builds,
but that adds a comical amount of time to the full cross platform build.

requirements.txt

@@ -5,7 +5,7 @@ certifi==2020.4.5.1
 cffi==1.15.0
 chardet==3.0.4
 click==8.0.3
-cryptography==36.0.1
+cryptography==3.3.2
 Flask==1.1.1
 Flask-Session==0.4.0
 idna==2.9