Tools: Update runplanetest.py to reflect reworded ground start messages

Tools/scripts/runplanetest.py

@@ -37,7 +37,7 @@ def wait_time(mav, simtime):
 
 cmd = 'sim_vehicle.py -j4 -D -f plane'
 mavproxy = pexpect.spawn(cmd, logfile=sys.stdout, timeout=30)
-mavproxy.expect("Ready to fly")
+mavproxy.expect("Ground start complete")
 
 mav = mavutil.mavlink_connection('127.0.0.1:14550')