[gnome-shell] shellMountOperation: Remove unused volume monitor

[Marge Bot <marge-bot src gnome org>]

commit 2e275cca25850a2016d00b4b3469eb8c38bdc017
Author: Sebastian Keller <skeller gnome org>
Date:   Wed Nov 3 20:53:55 2021 +0100

    shellMountOperation: Remove unused volume monitor
    
    It seems to have never been used since 6b5f9a647a, the commit that
    introduced it.
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2021>

 js/ui/shellMountOperation.js | 1 -
 1 file changed, 1 deletion(-)
---
diff --git a/js/ui/shellMountOperation.js b/js/ui/shellMountOperation.js
index 2956c0e967..d0d03491ff 100644
--- a/js/ui/shellMountOperation.js
+++ b/js/ui/shellMountOperation.js
@@ -542,7 +542,6 @@ var GnomeShellMountOpHandler = class {
                                        Gio.BusNameOwnerFlags.REPLACE, null, null);
 
         this._dialog = null;
-        this._volumeMonitor = Gio.VolumeMonitor.get();
 
         this._ensureEmptyRequest();
     }