OpenID Connect integration tests failing due to missing fixture Docker image

[mark-vieira]

It seems the c2id/c2id-server docker image has dissappeared from DockerHub so our idp-fixture that depends on it can no longer start. This is currently only required by our oidc-op-tests project so for now I've disabled these tests. We'll need to find an alternative fixture here. I tried simply replacing it with the c2id-server-demo image but it wasn't a direct replacement.

https://gradle-enterprise.elastic.co/s/p4vwhzkudvutw

[elasticsearchmachine]

Pinging @elastic/es-security (Team:Security)