shell/window-tracker: Do not filter tracked windows by type
The window-type property may change, and with it the skip-taskbar
property that decides whether we consider it "interesting".
As a result we can end up showing untracked window, i.e. one
which does not have an associated app.
Cover this case by simply tracking all windows regardless of
their type. This won't change the app's running state, as that
is solely based on the skip-taskbar property (which is enforced
for all previously excluded window types).