Bump cryptography from 2.8 to 3.2

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.8 to 3.2.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pyca/cryptography/compare/2.8...3.2)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -5,7 +5,7 @@ bleach==3.1.4
 certifi==2019.11.28
 cffi==1.14.0
 chardet==3.0.4
-cryptography==2.8
+cryptography==3.2
 cycler==0.10.0
 decorator==4.4.2
 defusedxml==0.6.0