Copter: remove paths for documenation for non-multi frame

Our current documentation system only emits one XML document (apm.pdef.xml)
for ArduCopter.

Since there is a conflict between parameters in the MOT_ namespace in Copter,
we only emit the documentation for the first parameter defining the MOT_ namespace.

This patch removes the documentation lines for frame types other than multicopter, meaning the documentation will reflect mutlictopter usage - the most common case.

These lines will need to be reinstated when we change the way we produce the xml documentation.

ArduCopter/Parameters.cpp

@@ -841,18 +841,12 @@ const AP_Param::Info Copter::var_info[] = {
     GOBJECT(motors, "H_",           AP_MotorsHeli_Single),
 
 #elif FRAME_CONFIG == SINGLE_FRAME
-    // @Group: MOT_
-    // @Path: ../libraries/AP_Motors/AP_MotorsSingle.cpp
     GOBJECT(motors, "MOT_",           AP_MotorsSingle),
 
 #elif FRAME_CONFIG == COAX_FRAME
-    // @Group: MOT_
-    // @Path: ../libraries/AP_Motors/AP_MotorsCoax.cpp
     GOBJECT(motors, "MOT_",           AP_MotorsCoax),
 
 #elif FRAME_CONFIG == TRI_FRAME
-    // @Group: MOT_
-    // @Path: ../libraries/AP_Motors/AP_MotorsTri.cpp
     GOBJECT(motors, "MOT_",           AP_MotorsTri),
 
 #else