On X11, the stage itself is backed by an XWindow, and moving the
input focus elsewhere will bypass any Clutter-level grabs.
This effectively allows newly opened windows to steal the focus
from gnome-shell itself, which is clearly undesirable. To prevent
that, only move the X11 focus when no grab is in place, just like
commit 50e89e376 did for the stage focus.
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/5932
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2776>