Conflict with older adwaita-gtk3-theme packages
    
    /usr/share/themes/Adwaita/gtk-3.0/gtk.css moved at one point from
    adwaita-gtk3-theme to gnome-themes-standard. Add explicit conflicts so
    that yum / dnf know to avoid the combination of old adwaita-gtk3-theme
    and new gnome-themes-standard instead of running into file conflicts.
    
    This should not happen during normal operation because
    adwaita-gtk3-theme is correctly obsoleted by gtk3. However, yum with
    --skip-broken can end up not pulling in gtk3 to the transaction set; in
    that case the explicit conflicts help it avoid the broken combination.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1133372