Don't apply _GTK_HIDE_TITLEBAR_WHEN_MAXIMIZED to tiled windows
This is not clear cut since tiled windows indeed set
_NET_WM_STATE_MAXIMIZED_VERT, but losing the titlebar when tiling two windows side-by-side makes almost impossible to discern which one has focus. Also, the main use case of hiding the titlebar is a kind of "zen mode" IMO, in which the user wants to both maximize screen space and minimize distraction (but still keeping an eye on important information on the top bar). Tiling is not part of this use case.