fix: use-after-move of bus connection in xdg portal detection (#47023)

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: deepak1556 <hop2deep@gmail.com>

shell/browser/ui/file_dialog_linux_portal.cc

@@ -86,8 +86,9 @@ void CheckPortalAvailabilityOnBusThread() {
                     << (g_portal_available ? "yes" : "no");
             flag->Set();
             bus->ShutdownAndBlock();
+            bus.reset();
           },
-          std::move(bus), flag));
+          bus, flag));
 }
 
 }  // namespace