Remove contact lookup

The contact lookup feature depends on libfolks

This has some issues right now:

• There has been discussions about perhaps retiring libfolks: folks#127
• e-d-s (which is a dependency of libfolks), now pulls in libsoup 3, meaning at the moment Maps doesn't start (running from git main), and we're stuck at libsoup 2 as long as we remain with libchamplain

Also, Contacts now supports opening Maps with a search request pointing to a contact's address (when it's set).

One suggestion is to remove this support for now, and possibly in the future re-implement it (using e-d-s directly?)