Remove unnecessary line from the font sample

This was mistakenly left over in the commit adding private fonts support
(547e40b114).

samples/font/font.cpp

@@ -389,7 +389,6 @@ bool MyApp::OnInit()
 {
     if ( !wxApp::OnInit() )
         return false;
-    wxString privfont = argv[0].BeforeLast('/');
 
     // Create the main application window
     MyFrame *frame = new MyFrame();