Remove pin on cryptography.

Author: domdfcoding

requirements.txt

@@ -1,6 +1,5 @@
 click>=7.1.2
 consolekit>=1.1.2
-cryptography==3.3.2; platform_system != "Linux"
 deprecation-alias>=0.2.0
 domdf-python-tools>=2.0.0
 dulwich!=0.20.7,!=0.20.8,!=0.20.9,>=0.20.5