Rename import to upgrade guide

Author: nabeel-nbcu

sidebars.js

@@ -17,9 +17,9 @@ module.exports = {
       items: [
         'installation/uploading',
         'installation/vhost',
+        'installation/upgrade-from-legacy',
         'installation/installation',
         'installation/cron',
-        'installation/importing',
         'installation/updating',
         'installation/issues',
       ]