Sub: Remove old RC-style arm and disarm checks

ArduSub/ArduSub.cpp

@@ -91,7 +91,6 @@ const AP_Scheduler::Task Sub::scheduler_tasks[] = {
 #endif
     SCHED_TASK(update_batt_compass,   10,    120),
     SCHED_TASK(read_aux_switches,     10,     50),
-    SCHED_TASK(arm_motors_check,      10,     50),
     SCHED_TASK(auto_disarm_check,     10,     50),
     SCHED_TASK(auto_trim,             10,     75),
 	SCHED_TASK(read_rangefinder,      20,    100),

ArduSub/Sub.h

@@ -852,7 +852,6 @@ private:
     bool mavlink_motor_test_check(mavlink_channel_t chan, bool check_rc);
     uint8_t mavlink_motor_test_start(mavlink_channel_t chan, uint8_t motor_seq, uint8_t throttle_type, uint16_t throttle_value, float timeout_sec);
     void motor_test_stop();
-    void arm_motors_check();
     void auto_disarm_check();
     bool init_arm_motors(bool arming_from_gcs);
     void update_arming_checks(void);