magnifier: Stop exposing D-Bus interface

Screen magnification is the compositor's business, not that of "random"
unprivileged tools. And for cases where a more specialised behavior is
wanted, an extension likely does a better job than a consumer of the
D-Bus API.

In addition to that, exporting the interface has been broken for an
unknown time, because the object that holds the implementation isn't
referenced and thus ends up being garbage collected, whoops.

And last but not least, this gets rid of the last public D-Bus name
that isn't clearly in the system namespace (org.gnome.Shell,
org.gnome.Mutter, org.gtk).

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3452

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1523>

js/ui/magnifier.js

@@ -7,7 +7,6 @@ const Signals = imports.signals;
 const Background = imports.ui.background;
 const FocusCaretTracker = imports.ui.focusCaretTracker;
 const Main = imports.ui.main;
-const MagnifierDBus = imports.ui.magnifierDBus;
 const Params = imports.misc.params;
 const PointerWatcher = imports.ui.pointerWatcher;
 
@@ -117,8 +116,6 @@ var Magnifier = class Magnifier {
             this.setActive(St.Settings.get().magnifier_active);
         });
 
-        // Export to dbus.
-        new MagnifierDBus.ShellMagnifier();
         this.setActive(St.Settings.get().magnifier_active);
     }