Reword MESH_G28_REST_ORIGIN comment

Marlin/Configuration.h

   #define MESH_NUM_Y_POINTS 3
   #define MESH_HOME_SEARCH_Z 4  // Z after Home, bed somewhere below but above 0.0.
 
-  //#define MESH_G28_REST_ORIGIN // Enable to make 'G28' all axis to rest at origin [0,0,0]
+  //#define MESH_G28_REST_ORIGIN // After homing all axes ('G28' or 'G28 XYZ') rest at origin [0,0,0]
 
   //#define MANUAL_BED_LEVELING  // Add display menu option for bed leveling.