ardupilotmega: MAV_CMD_GUIDED_CHANGE_ALTITUDE: correct alt rate-of-ch…

…ange unit

message_definitions/v1.0/ardupilotmega.xml

@@ -314,7 +314,7 @@
         <description>Change target altitude at a given rate. This slews the vehicle at a controllable rate between it's previous altitude and the new one. (affects GUIDED only. Outside GUIDED, aircraft ignores these commands. Designed for onboard companion-computer command-and-control, not normally operator/GCS control.)</description>
         <param index="1">Empty</param>
         <param index="2">Empty</param>
-        <param index="3" label="alt rate-of-change" units="m/s/s" minValue="0">Rate of change, toward new altitude. 0 for maximum rate change. Positive numbers only, as negative numbers will not converge on the new target alt.</param>
+        <param index="3" label="alt rate-of-change" units="m/s" minValue="0">Rate of change, toward new altitude. 0 for maximum rate change. Positive numbers only, as negative numbers will not converge on the new target alt.</param>
         <param index="4">Empty</param>
         <param index="5">Empty</param>
         <param index="6">Empty</param>