Bump cryptography from 2.3.1 to 3.2 in /requirements

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.3.1 to 3.2.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](pyca/cryptography@2.3.1...3.2)

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

requirements/requirements.txt

@@ -4,14 +4,13 @@
 #
 #    pip-compile --output-file requirements.txt requirements.in
 #
-asn1crypto==0.24.0        # via cryptography
 certifi==2018.10.15       # via requests
 cffi==1.11.5              # via cryptography
 chardet==3.0.4            # via requests
-cryptography==2.3.1       # via pyopenssl
-idna==2.7                 # via cryptography, requests
+cryptography==3.2         # via pyopenssl
+idna==2.7                 # via requests
 pycparser==2.19           # via cffi
-pyopenssl==18.0.0
-requests==2.20.0
+pyopenssl==18.0.0         # via -r requirements.in
+requests==2.20.0          # via -r requirements.in
 six==1.11.0               # via cryptography, pyopenssl
 urllib3==1.24             # via requests