AP_OpticalFlow: use ins singleton

libraries/AP_OpticalFlow/examples/AP_OpticalFlow_test/AP_OpticalFlow_test.cpp

@@ -27,7 +27,7 @@ public:
     AP_InertialSensor ins;
     AP_SerialManager serial_manager;
     RangeFinder sonar{serial_manager, ROTATION_PITCH_270};
-    AP_AHRS_NavEKF ahrs{ins, EKF2, EKF3, AP_AHRS_NavEKF::FLAG_ALWAYS_USE_EKF};
+    AP_AHRS_NavEKF ahrs{EKF2, EKF3, AP_AHRS_NavEKF::FLAG_ALWAYS_USE_EKF};
     NavEKF2 EKF2{&ahrs, sonar};
     NavEKF3 EKF3{&ahrs, sonar};
 };