Remove unused JSON_PREFIX constant

Change-Id: I7f5e7b74d765e5683dcd39131dcbfc12cf01b245
diff --git a/src/main/resources/static/gr-serviceuser-ssh-panel.js b/src/main/resources/static/gr-serviceuser-ssh-panel.js
index c12bace..e1e8dd0 100644
--- a/src/main/resources/static/gr-serviceuser-ssh-panel.js
+++ b/src/main/resources/static/gr-serviceuser-ssh-panel.js
@@ -18,8 +18,6 @@
 (function() {
   'use strict';
 
-  const JSON_PREFIX = ')]}\'';
-
   Polymer({
     is: 'gr-serviceuser-ssh-panel',
     _legacyUndefinedCheck: true,