AP_BattMonitor: fix parameters appearing in wiki param list erroneously

libraries/AP_BattMonitor/AP_BattMonitor_Params.cpp

@@ -62,7 +62,7 @@ const AP_Param::GroupInfo AP_BattMonitor_Params::var_info[] = {
     // @User: Standard
     AP_GROUPINFO("CAPACITY", 7, AP_BattMonitor_Params, _pack_capacity, 3300),
 
-    // @Param: WATT_MAX
+    // @Param{Plane}: WATT_MAX
     // @DisplayName: Maximum allowed power (Watts)
     // @Description: If battery wattage (voltage * current) exceeds this value then the system will reduce max throttle (THR_MAX, TKOFF_THR_MAX and THR_MIN for reverse thrust) to satisfy this limit. This helps limit high current to low C rated batteries regardless of battery voltage. The max throttle will slowly grow back to THR_MAX (or TKOFF_THR_MAX ) and THR_MIN if demanding the current max and under the watt max. Use 0 to disable.
     // @Units: W