Remove system.cron.js and libraries definition

17f3807f in 2010 (!) removed the last call to system.cron.js. There's no reason for it to be there. To add to the hilarity, 07ad6e73 two and a half years later (!) added the definition of this totally defunct JS file to system_library_info .

Please remove the JS, the definition and get the tests pass. The problematic test is core/modules/views/lib/Drupal/views/Tests/Plugin/CacheTest.php uses this file as a JS that shouldn't be added... please pick another, say core/modules/user/user.permissions.js .