Remove invalid keyboard_folder from gk6 (#16480)

keyboards/gizmo_engineering/gk6/info.json

@@ -1,6 +1,5 @@
 {
     "keyboard_name": "Gizmo Engineering GK6",
-    "keyboard_folder": "gk6",
     "url": "https://gizmo.engineering/",
     "maintainer": "federicoweber",
     "layouts": {