core-deps-latest: Don't build session manager for pipewire

Pipewire defaults to pipewire-media-session and will build that as a subproject by default. That session manager has a few issues since these days the default is wireplumber. Most people are not exactly interested in building wireplumber when building pipewire though and there's a separate jhbuild module for that anyway.

So let's disable building a session manager in pipewire and just use the one provided by the system, which is wireplumber these days.