ForeignToplevelManagerV1 now reports hidden window handles instead of…

… purposefully hiding them (#3380)

When we switch workspaces, foreign top level was reporting different
windows, which doesn't seem right. The spec doesn't specify whether or
not hidden windows should be reported.

src/server/frontend_wayland/foreign_toplevel_manager_v1.cpp

@@ -357,7 +357,6 @@ void mf::ForeignSurfaceObserver::create_or_close_toplevel_handle_as_needed(std::
         switch(surface->state())
         {
         case mir_window_state_attached:
-        case mir_window_state_hidden:
             should_have_handle = false;
             break;