Remove dead code

ScriptableRenderPipeline/HDRenderPipeline/ShaderPass/ShaderPassForward.hlsl

 #endif
 }
 
-
-float4 ApplyBlendModePerserveSpecularLighting(float3 diffuseLighting, float3 specularLighting, float opacity)
-{
-
-}
-
 void Frag(PackedVaryingsToPS packedInput,
           out float4 outColor : SV_Target0
       #ifdef _DEPTHOFFSET_ON