Update heights of POM materials to match the tessellated versions

Assets/TestScenes/HDTest/GraphicTest/Parallax Occlusion Mapping/Material/POM - Rock.mat

     - _GlossMapScale: 1
     - _Glossiness: 0.5
     - _GlossyReflections: 1
-    - _HeightAmplitude: 0.09
+    - _HeightAmplitude: 0.8
     - _HeightCenter: 0.5
     - _HorizonFade: 1
     - _MaterialID: 0

Assets/TestScenes/HDTest/GraphicTest/Parallax Occlusion Mapping/Material/POM - Wood.mat

     - _GlossMapScale: 1
     - _Glossiness: 0.5
     - _GlossyReflections: 1
-    - _HeightAmplitude: 0.17
+    - _HeightAmplitude: 1.27
     - _HeightCenter: 0.5
     - _HorizonFade: 1
     - _MaterialID: 0