Deprecation warning for dhcrypto and Python 3.6

```text
/usr/lib/python3/dist-packages/secretstorage/dhcrypto.py:15: CryptographyDeprecationWarning: Python 3.6 is no longer supported by the Python core team. Therefore, support for it is deprecated in cryptography. The next release of cryptography will remove support for Python 3.6.
  from cryptography.utils import int_from_bytes
```

In `dotnet-runtime-perf` and related.