ArduPlane: removed set_blocking_writes_all calls

ArduPlane/system.cpp

@@ -195,11 +195,6 @@ void Plane::startup_ground(void)
     // reset last heartbeat time, so we don't trigger failsafe on slow
     // startup
     gcs().sysid_myggcs_seen(AP_HAL::millis());
-
-    // we don't want writes to the serial port to cause us to pause
-    // mid-flight, so set the serial ports non-blocking once we are
-    // ready to fly
-    serial_manager.set_blocking_writes_all(false);
 }