Vehicle: ignore severity of PX4 preflight messages

We had someone change this condition out of confusion downstream and I figured out there is no message with emergency severity containing the string "preflight" in the current PX4 version. I can still check if and where they might have existed on older versions but I'd suggest to remove this since for the events it doesn't make sense to sort the text by severity.

src/Vehicle/Vehicle.cc

@@ -3997,7 +3997,7 @@ void Vehicle::_textMessageReceived(MAV_COMPONENT componentid, MAV_SEVERITY sever
 
     bool skipSpoken = false;
     const bool ardupilotPrearm = text.startsWith(QStringLiteral("PreArm"));
-    const bool px4Prearm = text.startsWith(QStringLiteral("preflight"), Qt::CaseInsensitive) && (severity >= MAV_SEVERITY::MAV_SEVERITY_CRITICAL);
+    const bool px4Prearm = text.startsWith(QStringLiteral("preflight"), Qt::CaseInsensitive);
     if (ardupilotPrearm || px4Prearm) {
         auto eventData = _events.find(componentid);
         if (eventData != _events.end()) {