GPS: Remove unnecessary warning message

This warning message would often be printed during normal configuration and does not represent a good indicator for true GPS lost states. Instead the system flags should be used, which are available through the normal logging system.

src/drivers/gps/gps.cpp

@@ -769,7 +769,6 @@ GPS::run()
 				}
 
 				if (_healthy) {
-					PX4_WARN("GPS module lost");
 					_healthy = false;
 					_rate = 0.0f;
 					_rate_rtcm_injection = 0.0f;