Update Sub Graph Importer version

com.unity.shadergraph/Editor/Importers/ShaderSubGraphImporter.cs

 using System.Linq;
 using System.Text;
 
-[ScriptedImporter(1, "ShaderSubGraph")]
+[ScriptedImporter(2, "ShaderSubGraph")]
 public class ShaderSubGraphImporter : ScriptedImporter
 {
     public override void OnImportAsset(AssetImportContext ctx)