AP_Math: tests: correct tested return value for limit_accel_xy

in this corner case we *do* need to scale the vector

libraries/AP_Math/tests/test_control.cpp

@@ -509,7 +509,7 @@ TEST(Control, test_limit_accel)
         signal_caught = true;
     } else {
         // we come through here normally
-        EXPECT_FALSE(limit_accel_xy(vel, accel, accel_max));
+        EXPECT_TRUE(limit_accel_xy(vel, accel, accel_max));
     }
 
     EXPECT_FALSE(signal_caught);