updated lightweight standard material

ScriptableRenderPipeline/LightweightPipeline/Materials/Lightweight-StandardShader.mat

   m_PrefabInternal: {fileID: 0}
   m_Name: Lightweight-StandardShader
   m_Shader: {fileID: 4800000, guid: 933532a4fcc9baf4fa0491de14d08ed7, type: 3}
-  m_ShaderKeywords: _METALLIC_SETUP
+  m_ShaderKeywords: 
   m_LightmapFlags: 4
   m_EnableInstancingVariants: 0
   m_DoubleSidedGI: 0