Fix harmless warning about unused variable in isosurf sample.

Don't declare and initialize a variable that we never use.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68110 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/opengl/isosurf/isosurf.cpp

@@ -57,7 +57,7 @@ bool MyApp::OnInit()
         return false;
 
     // Create the main frame window
-    MyFrame *frame = new MyFrame(NULL, wxT("wxWidgets OpenGL Isosurf Sample"));
+    new MyFrame(NULL, wxT("wxWidgets OpenGL Isosurf Sample"));
 
     return true;
 }