
In commit 1218e68
we allowed full-sized window previews under the
assumption that we had enough other clues (like the vignette effect)
to differentiate the overview from the regular session.
That didn't hold up in testing, so make the maximum preview size
slightly smaller again.
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3464
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1525>