Revert "onroad UI: show negative speed (#23987)"

This reverts commit cac807daf9e39f982db2a856403a50a67622b992.

old-commit-hash: de56544531

selfdrive/ui/qt/onroad.cc

@@ -186,7 +186,7 @@ void OnroadHud::updateState(const UIState &s) {
     maxspeed *= KM_TO_MILE;
   }
   QString maxspeed_str = cruise_set ? QString::number(std::nearbyint(maxspeed)) : "N/A";
-  float cur_speed = sm["carState"].getCarState().getVEgo() * (s.scene.is_metric ? MS_TO_KPH : MS_TO_MPH);
+  float cur_speed = std::max(0.0, sm["carState"].getCarState().getVEgo() * (s.scene.is_metric ? MS_TO_KPH : MS_TO_MPH));
 
   setProperty("is_cruise_set", cruise_set);
   setProperty("speed", QString::number(std::nearbyint(cur_speed)));