Fix off by one pixel error when drawing active tab in wxAUI.

The active tab had a drawing artefact because its gradient background was
drawn in a rectangle one pixel too short.

See #11411.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67427 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/aui/auibook.cpp

@@ -455,7 +455,7 @@ void wxAuiDefaultTabArt::DrawTab(wxDC& dc,
         // set rectangle down a bit for gradient drawing
         r.SetHeight(r.GetHeight()/2);
         r.x += 2;
-        r.width -= 2;
+        r.width -= 3;
         r.y += r.height;
         r.y -= 2;