Fix link to nanodet documentation (#421)

* Fix link to nanodet documentation

* Fix extension

docs/reference/index.md

@@ -43,7 +43,7 @@ Neither the copyright holder nor any applicable licensor will be liable for any
             - [edgespeechnets Module](edgespeechnets.md)
             - [quadraticselfonn Module](quadratic-selfonn.md)
         - object detection 2d:
-            - [nanodet Module](nanodet.md)
+            - [nanodet Module](object-detection-2d-nanodet.md)
             - [detr Module](detr.md)
             - [gem Module](gem.md)
             - [retinaface Module](face-detection-2d-retinaface.md)