bus-proxyd: --user -- add Accept=yes to socket
core: do not add implicit dbus.socket dependency

Sockets are ordered before sockets.target anyway, and sockets.target
is ordered before basic.target, and hence all bus services end up
being ordered after dbus.socket anyway. Since for kdbus clients
dbus.socket is obsolete, let's not add this dependency explicitly.

Also, it's hot in Australia and we are going for breakfast now.