screen: Remove auto-minimization "feature"

https://bugzilla.gnome.org/show_bug.cgi?id=705177
Revert "display: Don't put minimized windows at the back of alt-tab"

This reverts commit 7e61ef09369a6564ad51d9d654db0e3d104fe0fc.

https://bugzilla.gnome.org/show_bug.cgi?id=705177