common.xml: Do not deprecate MAV_CMD_NAV_FENCE_RETURN_POINT. it is he…

…avily used by Ardupilot (mavlink#1539)

Co-authored-by: Hamish Willee <[email protected]>

message_definitions/v1.0/common.xml

@@ -1967,7 +1967,6 @@
         <param index="7" label="Altitude" units="m">Altitude</param>
       </entry>
       <entry value="5000" name="MAV_CMD_NAV_FENCE_RETURN_POINT" hasLocation="true" isDestination="true">
-        <deprecated since="2020-09" replaced_by="MAV_CMD_NAV_RALLY_POINT">This mechanism was superseded by rally points. If rally points are defined then they take precedence.</deprecated>
         <description>Fence return point. There can only be one fence return point.
         </description>
         <param index="1">Reserved</param>