[gnome-shell] workspaceThumbnail: Remove this.actor definition to ThumbnailsBox

[Florian Müllner <fmuellner src gnome org>]

commit 44fcb9e9afe6a70f772afd1677c131b08f496d6a
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Tue Apr 9 18:26:39 2019 -0500

    workspaceThumbnail: Remove this.actor definition to ThumbnailsBox
    
    Remove this.actor = actor, since the class is now an actor itself.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/487

 js/ui/workspaceThumbnail.js | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
---
diff --git a/js/ui/workspaceThumbnail.js b/js/ui/workspaceThumbnail.js
index 73cf7b4d1..969167178 100644
--- a/js/ui/workspaceThumbnail.js
+++ b/js/ui/workspaceThumbnail.js
@@ -601,8 +601,7 @@ class ThumbnailsBox extends St.Widget {
                       style_class: 'workspace-thumbnails',
                       request_mode: Clutter.RequestMode.WIDTH_FOR_HEIGHT });
 
-        this.actor = this;
-        this.actor._delegate = this;
+        this._delegate = this;
 
         let indicator = new St.Bin({ style_class: 'workspace-thumbnail-indicator' });