comment - use markdown in replaced by to fix rendering (mavlink#2137)

Author: hamishwillee

message_definitions/v1.0/common.xml

@@ -1254,7 +1254,7 @@
         <param index="7" label="Altitude/Z">Center point altitude (MSL) (if no MAV_FRAME specified) / Z coordinate according to MAV_FRAME. NaN: Use current vehicle altitude.</param>
       </entry>
       <entry value="80" name="MAV_CMD_NAV_ROI" hasLocation="true" isDestination="false">
-        <deprecated since="2018-01" replaced_by="MAV_CMD_DO_SET_ROI_*"/>
+        <deprecated since="2018-01" replaced_by="`MAV_CMD_DO_SET_ROI_*`"/>
         <description>Sets the region of interest (ROI) for a sensor set or the vehicle itself. This can then be used by the vehicle's control system to control the vehicle attitude and the attitude of various sensors such as cameras.</description>
         <param index="1" label="ROI Mode" enum="MAV_ROI">Region of interest mode.</param>
         <param index="2" label="WP Index" minValue="0" increment="1">Waypoint index/ target ID. (see MAV_ROI enum)</param>
@@ -1661,7 +1661,7 @@
         <param index="7">Empty</param>
       </entry>
       <entry value="201" name="MAV_CMD_DO_SET_ROI" hasLocation="true" isDestination="false">
-        <deprecated since="2018-01" replaced_by="MAV_CMD_DO_SET_ROI_*"/>
+        <deprecated since="2018-01" replaced_by="`MAV_CMD_DO_SET_ROI_*`"/>
         <description>Sets the region of interest (ROI) for a sensor set or the vehicle itself. This can then be used by the vehicle's control system to control the vehicle attitude and the attitude of various sensors such as cameras.</description>
         <param index="1" label="ROI Mode" enum="MAV_ROI">Region of interest mode.</param>
         <param index="2" label="WP Index" minValue="0" increment="1">Waypoint index/ target ID (depends on param 1).</param>
@@ -1706,7 +1706,7 @@
       </entry>
       <!-- this one is messed up! altitude should be param 7, not param4 -->
       <entry value="205" name="MAV_CMD_DO_MOUNT_CONTROL" hasLocation="false" isDestination="false">
-        <deprecated since="2020-01" replaced_by="MAV_CMD_DO_GIMBAL_MANAGER_PITCHYAW">This message is ambiguous and inconsistent. It has been superseded by MAV_CMD_DO_GIMBAL_MANAGER_PITCHYAW and MAV_CMD_DO_SET_ROI_*. The message can still be used to communicate with legacy gimbals implementing it.</deprecated>
+        <deprecated since="2020-01" replaced_by="MAV_CMD_DO_GIMBAL_MANAGER_PITCHYAW">This message is ambiguous and inconsistent. It has been superseded by MAV_CMD_DO_GIMBAL_MANAGER_PITCHYAW and `MAV_CMD_DO_SET_ROI_*` variants. The message can still be used to communicate with legacy gimbals implementing it.</deprecated>
         <description>Mission command to control a camera or antenna mount</description>
         <param index="1" label="Pitch">pitch depending on mount mode (degrees or degrees/second depending on pitch input).</param>
         <param index="2" label="Roll">roll depending on mount mode (degrees or degrees/second depending on roll input).</param>
@@ -2731,7 +2731,7 @@
       </entry>
     </enum>
     <enum name="MAV_ROI">
-      <deprecated since="2018-01" replaced_by="MAV_CMD_DO_SET_ROI_*"/>
+      <deprecated since="2018-01" replaced_by="`MAV_CMD_DO_SET_ROI_*`"/>
       <description>The ROI (region of interest) for the vehicle. This can be
                 be used by the vehicle for camera/vehicle attitude alignment (see
                 MAV_CMD_NAV_ROI).</description>