Fixes T11222. This was lazy-future-proofed for Conduit SSH support, but users are boundlessly creative. Check protocols explicitly.
$ arc install-certificate a.b:1/ Usage Exception: Server URI "a.b:1/" must include the "http" or "https" protocol. It should be in the form "https://phabricator.example.com/".
- Also went through a successful workflow with a URI in the form provided in the example.