Remove wxGTK-specific text shift in wxRenderer::DrawHeaderButtonContents().

This was probably related to the code removed by r63947 and doesn't seem to be
needed here neither (and could presumably result in the same problems as in
the ticket #11780).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64306 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/renderg.cpp

@@ -386,9 +386,6 @@ wxRendererGeneric::DrawHeaderButtonContents(wxWindow *win,
         dc.GetTextExtent( label, &tw, &th, &td);
         labelWidth += tw;
         y = rect.y + wxMax(0, (rect.height - (th+td)) / 2);
-#ifdef __WXGTK__
-        y += 2; // No idea why.
-#endif
 
         // truncate and add an ellipsis (...) if the text is too wide.
         int targetWidth = rect.width - arrowSpace - bmpWidth - 2*margin;