HDRenderLoop: Fix issue with alpha test

Assets/ScriptableRenderLoop/HDRenderLoop/Shaders/TemplateDisneyGGX.hlsl

 // float _CoatRoughness;
 // sampler2D _CoatRoughnessMap;
 
-float _Cutoff;
+float _AlphaCutoff;
 
 //-------------------------------------------------------------------------------------
 // Lighting architecture
 #endif
 
 #ifdef _ALPHATEST_ON
-	clip(alpha - _Cutoff);
+	clip(alpha - _AlphaCutoff);
 #endif
 
 	builtinData.opacity = alpha;