Replace the link to the Biwi Kinect Head Pose Database

Sadly, it appears that ETH Zürich took this dataset down. The best thing
we can do now is to point to the dataset index page.

Author: Roman Donchenko

models/intel/head-pose-estimation-adas-0001/description/head-pose-estimation-adas-0001.md

@@ -8,7 +8,7 @@ one output.
 
 ## Validation Dataset
 
-[Biwi Kinect Head Pose Database](https://data.vision.ee.ethz.ch/cvl/gfanelli/head_pose/head_forest.html)
+[Biwi Kinect Head Pose Database](https://www.vision.ee.ethz.ch/en/datasets/)
 
 ## Example