Seems like older versions lack part of the api we're using in
briar_wrapper.

Linux Mint 19.1 Tessa is still on websockets version 3.4, so we should
really require a more recent version here.

First steps analogous to
https://salsa.debian.org/xmpp-team/sms4you/-/commit/6dcf2ccc13d4d2f962fafb96ba9a9ac54ce9fa18.