Firmwareplugin: Trim retry period to something that matches closer the users...

Firmwareplugin: Trim retry period to something that matches closer the users attention and is still long enough to allow for multiple heartbeats to pass through

src/FirmwarePlugin/FirmwarePlugin.cc

@@ -485,7 +485,7 @@ bool FirmwarePlugin::_setFlightModeAndValidate(Vehicle* vehicle, const QString&
         vehicle->setFlightMode(flightMode);
 
         // Wait for vehicle to return flight mode
-        for (int i=0; i<30; i++) {
+        for (int i=0; i<22; i++) {
             if (vehicle->flightMode() == flightMode) {
                 flightModeChanged = true;
                 break;