There's little point in setting properties to their default value,
so stop doing that.
(GtkFrame:shadow-type actually defaults to "edged-in" rather than "in",
but all types other than "none" are treated the same nowadays)
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1495>
As outlined earlier, in order to turn the Extensions app into a properly
sandboxed application, we need to split out the extension prefs dialog
and move it elsewhere.
With "elsewhere" being the new Extensions D-Bus service, effectively
turning it into a shell extensions portal.
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1106