Remove test case Verifier 11

[OR13]

11. The Verifier's Verify Credential HTTP API MUST adhere to the proof verification format.

This is essentially a dupe fo the first test... it amounts to "does verification succeed".

[OR13]

may also be a dupe of 13. The Verifier\'s Verify Credential HTTP API MUST support the verification of, JSON-LD Proof, Ed25519Signature2018.

[mavarley]

Agreed it may be a dupe (not sure if it is catching a subtly or not) but does removing this req. make the test suite easier to implement? Or is it just "removing noise" from the reqs?
(just wondering why it is marked 'critical').

[OR13]

@mavarley yes, changes to the test suite need comments! I marked them as critical before we had a release target.

[OR13]

We resolved to only rely on did:key for testing, and there are a number of fixtures that should be removed, per that and related resolutions.