removed unused uniform

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/InputSurface.hlsl

 half _Cutoff;
 half _Glossiness;
 half _GlossMapScale;
-half _SmoothnessTextureChannel;
 half _Metallic;
 half _BumpScale;
 half _OcclusionStrength;