Bump cryptography from 2.4.2 to 3.3.2 in /requirements

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.4.2 to 3.3.2.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/main/CHANGELOG.rst)
- [Commits](pyca/cryptography@2.4.2...3.3.2)

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

Author: dependabot[bot]

requirements/base.txt

@@ -11,7 +11,7 @@ bleach==1.4
 boto==2.38.0
 celery==3.1.19
 certifi==2015.04.28
-cryptography==2.4.2
+cryptography==3.3.2
 dj-database-url==0.3.0
 djrill==1.4.0
 djangoajax==2.2.15