Fem: modernize C++: return braced init list

src/Mod/Fem/Gui/ViewProviderFemPostPipelinePyImp.cpp

@@ -33,7 +33,7 @@ using namespace FemGui;
 // returns a string which represents the object e.g. when printed in python
 std::string ViewProviderFemPostPipelinePy::representation() const
 {
-    return std::string("<ViewProviderFemPostPipeline object>");
+    return {"<ViewProviderFemPostPipeline object>"};
 }
 
 PyObject *ViewProviderFemPostPipelinePy::updateColorBars(PyObject *args)