AP_OpticalFlow: fix _ENABLE param desc for stable release

libraries/AP_OpticalFlow/OpticalFlow.cpp

@@ -83,7 +83,7 @@ const AP_Param::GroupInfo OpticalFlow::var_info[] = {
     AP_GROUPINFO("_ADDR", 5,  OpticalFlow, _address,   0),
 
     // the parameter description below is for GCSs (like MP) that use master for the parameter descriptions.  This should be removed when Copter-3.7 is released
-    // @Param: _TYPE
+    // @Param: _ENABLE
     // @DisplayName: Optical flow enable/disable
     // @Description: Setting this to Enabled(1) will enable optical flow. Setting this to Disabled(0) will disable optical flow
     // @Values: 0:Disabled, 1:Enabled