[Keyboard] move niu_mini to /kbdfans (#16112)

keyboards/kbdfans/niu_mini/readme.md

@@ -10,10 +10,10 @@ Hardware Availability: [KBDFans](https://kbdfans.myshopify.com/products/niu-mini
 
 Make example for this keyboard (after setting up your build environment):
 
-    make niu_mini:default
+    make kbdfans/niu_mini:default
 
 Flashing example for this keyboard ([using the command line](https://docs.qmk.fm/#/newbs_flashing?id=flash-your-keyboard-from-the-command-line)):
 
-    make niu_mini:default:flash
+    make kbdfans/niu_mini:default:flash
 
 See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).