Issue 5028 - Use browser namespace

lib/firefoxDataCleanup.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 59 matching lines @@
       haveHitCounts.push(filter);
   }
 
   // Reset hit statistics on any filters having them
   FilterStorage.resetHitCounts(haveHitCounts);
 
   // Remove any existing automatic backups
   let backups = [];
   for (let i = 1; i < 100; i++)
     backups.push(`file:patterns-backup${i}.ini`);
-  browser.storage.local.remove(backups).then(() =>
+  browser.storage.local.remove(backups, () =>
   {
     Prefs.data_cleanup_done = true;
   });
 });