added missing comment of RGB control keys planck/rev6 (#6503)

keyboards/planck/keymaps/default/keymap.c

@@ -152,8 +152,9 @@ const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
 ),
 
 /* Adjust (Lower + Raise)
- * ,-----------------------------------------------------------------------------------.
- * |      | Reset|      |      |      |      |      |      |      |      |      |  Del |
+ *                      v------------------------RGB CONTROL--------------------v
+ * ,-----------------------------------------------------------------------------------
+ * |      | Reset|Debug | RGB  |RGBMOD| HUE+ | HUE- | SAT+ | SAT- |BRGTH+|BRGTH-|  Del |
  * |------+------+------+------+------+------+------+------+------+------+------+------|
  * |      |      |      |Aud on|Audoff|AGnorm|AGswap|Qwerty|Colemk|Dvorak|Plover|      |
  * |------+------+------+------+------+------+------+------+------+------+------+------|