[gnome-documents] preview: remove unused variable

[Cosimo Cecchi <cosimoc src gnome org>]

commit 74a4fdfa95ce6e1cbc8dd076fa22dc9ed1e1bab7
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Sun May 21 17:22:03 2017 -0700

    preview: remove unused variable

 src/preview.js |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)
---
diff --git a/src/preview.js b/src/preview.js
index 027334d..5f753e5 100644
--- a/src/preview.js
+++ b/src/preview.js
@@ -559,7 +559,6 @@ const PreviewNavControls = new Lang.Class({
 
         this._visible = false;
         this._visibleInternal = false;
-        this._pageChangedId = 0;
         this._autoHideId = 0;
         this._motionId = 0;