Revert "Put tabs at the bottom"

This reverts commit c6ee7553.

We have gotten feedback that this experiment was not liked by users,
so reverting.

src/nautilus-notebook.c

@@ -240,7 +240,6 @@ nautilus_notebook_init (NautilusNotebook *notebook)
 	gtk_notebook_set_scrollable (GTK_NOTEBOOK (notebook), TRUE);
 	gtk_notebook_set_show_border (GTK_NOTEBOOK (notebook), FALSE);
 	gtk_notebook_set_show_tabs (GTK_NOTEBOOK (notebook), FALSE);
-	gtk_notebook_set_tab_pos (GTK_NOTEBOOK (notebook), GTK_POS_BOTTOM);
 
 	g_signal_connect (notebook, "button-press-event",
 			  (GCallback)button_press_cb, NULL);