Revert "raise floating windows when focusing (Thanks Marcos)"

Revert "raise floating windows when focusing (Thanks Marcos)"

This commit breaks floating window keyboard focus order
(t/135-floating-focus.t) when you have > 2 floating windows. Since
keyboard focus is more important than saving one click to raise floating
windows, I revert the commit.

Note that we cannot implement this without keeping a third list (beneath
floating_windows and focus) for the z coordinate of a floating window.
This seems not worth it.

This reverts commit 064be457e59603e1d4a4b45b4bf138dcc231a849.