Remove Apostille-specific code from quay codebase

Now that Apostille has been shut down in quay.io we should review any Apostille-specific code still in the quay codebase and remove it. This signing feature has never been a supported feature in Red Hat Quay so on-premise customers should not be using it.

We can focus only on the non UI code found- there is no need to actually remove the code from our web UI as it's getting rewritten.