Revert a change to fix installer window interaction
    
    We found that this commit causes a bug where, sometimes, you
    can't interact with windows in the installer's advanced
    partitioning mode. Reverting this change means drop shadows are
    again considered part of a window's target area for clicking,
    but that seems like much less of a problem than "sometimes you
    can't click on anything at all".
    
    https://bugzilla.redhat.com/show_bug.cgi?id=2239128