Fix calls to `Path.Combine` that didn't work on Legacy scripting backend

ScriptableRenderPipeline/LightweightPipeline/LWRP/Editor/ShaderGraph/LightWeightPBRSubShader.cs

 
         static string GetTemplatePath(string templateName)
         {
-            string relativeTemplatePath = Path.Combine("LWRP", Path.Combine("Editor", Path.Combine("ShaderGraph", Path.Combine(templateName))));
+            string relativeTemplatePath = Path.Combine("LWRP", Path.Combine("Editor", Path.Combine("ShaderGraph", templateName)));
             foreach (var path in LightweightIncludePaths.GetPaths())
             {
                 var templatePath = Path.Combine(path, relativeTemplatePath);

ScriptableRenderPipeline/LightweightPipeline/LWRP/Editor/ShaderGraph/LightWeightUnlitSubShader.cs

 
         static string GetTemplatePath(string templateName)
         {
-            string relativeTemplatePath = Path.Combine("LWRP", Path.Combine("Editor", Path.Combine("ShaderGraph", Path.Combine(templateName))));
+            string relativeTemplatePath = Path.Combine("LWRP", Path.Combine("Editor", Path.Combine("ShaderGraph", templateName)));
             foreach (var path in LightweightIncludePaths.GetPaths())
             {
                 var templatePath = Path.Combine(path, relativeTemplatePath);