Remove /fingerprint endpoint

[kixelated]

Currently, WebTransport in Chrome does not accept self-signed certificates, even if they're from a local root. The work-around is to use the serverCertificateHash field when establishing the connection to explicitly list which certs are accepted. The certificate MUST use ECDSA and be valid for <14 days.

This is really annoying. The current approach is to host a /fingerprint endpoint on the server. The client issues a HTTPS request (yes, using the same cert) to get the cert before then connecting via WebTransport. It doubles the TLS handshakes and round trips. It also means the certificate has to be regenerated every week or two.