complement test image disables HTTP cert checking

[richvdh]

The image we build to run under complement disables HTTP cert checking for federation connections:

https://github.com/matrix-org/complement/blob/master/dockerfiles/synapse/homeserver.yaml#L44-L46

@kegsay suggests we don't do anything about this until matrix-org/complement#65 is fixed

[kegsay]

In theory you can now start doing this as of matrix-org/complement#299 - ca.crt and ca.key are always mounted to the container now, and COMPLEMENT_CA is no longer A Thing. The location of these files is subject to change as per matrix-org/complement#233 but for now they sit where they always have: /ca.

[richvdh]

I had a go at sorting this, but stumbled into matrix-org/complement#355, which is going to be a blocker.