Remove all wxS() macros from samples

The use of wxS() is an optimization which can be used to avoid an
implicit conversion from narrow to wide strings, but such optimizations
are not really needed in the samples and just make their code less
readable, so remove them.

Closes https://github.com/wxWidgets/wxWidgets/pull/956

samples/text/text.cpp

@@ -455,7 +455,7 @@ bool MyApp::OnInit()
         return false;
 
     // Create the main frame window
-    MyFrame *frame = new MyFrame(wxS("Text wxWidgets sample"), 50, 50);
+    MyFrame *frame = new MyFrame("Text wxWidgets sample", 50, 50);
 
     wxMenu *file_menu = new wxMenu;
     file_menu->Append(TEXT_SAVE, "&Save file\tCtrl-S",