Update Boards.h for Vellemann K8200 - comment only

## Update Boards.h for Vellemann K8200 - comment only

* Boards.h: updated comment for board 3Drag - K8200 uses same board

Marlin/boards.h

 #define BOARD_ULTIMAKER         7    // Ultimaker
 #define BOARD_ULTIMAKER_OLD     71   // Ultimaker (Older electronics. Pre 1.5.4. This is rare)
 #define BOARD_ULTIMAIN_2        72   // Ultimainboard 2.x (Uses TEMP_SENSOR 20)
-#define BOARD_3DRAG             77   // 3Drag Controller
+#define BOARD_3DRAG             77   // 3Drag Controller / Vellemann K8200 Controller
 #define BOARD_TEENSYLU          8    // Teensylu
 #define BOARD_RUMBA             80   // Rumba
 #define BOARD_PRINTRBOARD       81   // Printrboard (AT90USB1286)