Revert "AP_HAL: add force_safety_on method"

This reverts commit 033b14db16e18c297e04819feab54f0899a1baf4.
Revert "HAL_PX4: implement force_safety_on"

This reverts commit ffcd259b4e1b31f5583b9da268743010a1bf2b80.
Revert "HAL_VRBrain: implement force_safety_on"

This reverts commit 6da14205415834108426249c03609334e7f01abd.