autotest: remove default value for ARMING_RUDDER in blimp

this was ineffective as Blimp was not enforcing the parameter.  We do now

Author: peterbarker

Tools/autotest/default_params/blimp.parm

@@ -83,7 +83,6 @@ INS_ACC3SCAL_X   1.000
 INS_ACC3SCAL_Y   1.000
 INS_ACC3SCAL_Z   1.000
 
-ARMING_RUDDER 0
 GCS_PID_MASK 255
 SIM_SERVO_SPEED 0.06
 LOG_BITMASK      65535