Remove useless border style check from wxVListBox::Create()

The comparison could never be true as wxDEFAULT is not one of
wxBORDER_XXX values and so is not included in wxBORDER_MASK and so was
useless -- and just results in -Wtautological-compare from gcc 8.

Simply remove this check, a047aff270 added
it apparently to use themed border by default for wxVListBox, but this
was done in a better way in 28319afe55.

src/generic/vlbox.cpp

@@ -79,11 +79,6 @@ bool wxVListBox::Create(wxWindow *parent,
                         long style,
                         const wxString& name)
 {
-#ifdef __WXMSW__
-    if ( (style & wxBORDER_MASK) == wxDEFAULT )
-        style |= wxBORDER_THEME;
-#endif
-
     style |= wxWANTS_CHARS | wxFULL_REPAINT_ON_RESIZE;
     if ( !wxVScrolledWindow::Create(parent, id, pos, size, style, name) )
         return false;