crypton-x509's test suite depends on x509

[ysangkok]

I think it would be better if the test suite depended on crypton-x509 instead of x509.

See:

https://github.com/kazu-yamamoto/crypton-certificate/blob/main/x509/crypton-x509.cabal#L57

This caused tests to get disabled in Stackage, see build-constraints.yaml.

[kazu-yamamoto]

I have released a new version which uses crypton-x509 for testing.