Autotest: copter: fix wait_for_alt for descending wait

Tools/autotest/arducopter.py

@@ -138,9 +138,6 @@ class AutoTestCopter(AutoTest):
 
     def wait_for_alt(self, alt_min=30, timeout=30):
         """Wait for altitude to be reached."""
-        m = self.mav.recv_match(type='GLOBAL_POSITION_INT', blocking=True)
-        alt = m.relative_alt / 1000.0 # mm -> m
-        if alt < alt_min:
         self.wait_altitude(alt_min - 1,
                            (alt_min + 5),
                            relative=True,