[polari] urlPreview: Define exported class as var

[Florian Müllner <fmuellner src gnome org>]

commit da6d977d0cd6891a169df0d00d4459d521aa1e97
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Dec 19 04:40:12 2019 +0100

    urlPreview: Define exported class as var

 src/urlPreview.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/urlPreview.js b/src/urlPreview.js
index cf7e814..b6e7997 100644
--- a/src/urlPreview.js
+++ b/src/urlPreview.js
@@ -65,7 +65,7 @@ class Thumbnailer {
     }
 }
 
-let URLPreview = GObject.registerClass({
+var URLPreview = GObject.registerClass({
     Properties: {
         'uri': GObject.ParamSpec.string(
             'uri', 'uri', 'uri',