chore: remove hashIndex from t6 json material as it is always 0

src/ObjWriting/Game/T6/Material/DumperMaterialT6.cpp

@@ -30,5 +30,6 @@ void AssetDumperMaterial::DumpAsset(AssetDumpingContext& context, XAssetInfo<Mat
 
     const auto* material = asset->Asset();
     assert(material->info.gameFlags < 0x8000);
+    assert(material->info.hashIndex == 0);
     DumpMaterialAsJson(*assetFile, *material, context);
 }

src/ObjWriting/Material/JsonMaterialWriter.cpp.template

@@ -315,7 +315,6 @@ namespace
             jMaterial.surfaceTypeBits = material.info.surfaceTypeBits;
 #ifdef FEATURE_T6
             jMaterial.layeredSurfaceTypes = material.info.layeredSurfaceTypes;
-            jMaterial.hashIndex = material.info.hashIndex;
             jMaterial.surfaceFlags = material.info.surfaceFlags;
             jMaterial.contents = material.info.contents;
 #endif