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](pyca/cryptography@2.8...3.2)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

dev-requirements.txt

@@ -10,7 +10,7 @@ babel==2.8.0              # via sphinx
 certifi==2019.11.28       # via requests
 cffi==1.14.0              # via cryptography
 chardet==3.0.4            # via requests
-cryptography==2.8         # via -r dev-requirements.in
+cryptography==3.2         # via -r dev-requirements.in
 cython==0.29.15           # via -r dev-requirements.in
 docutils==0.16            # via sphinx
 entrypoints==0.3          # via flake8