Improve documentation for backup_restore.md

doc/raketasks/backup_restore.md

@@ -257,19 +257,22 @@ Users of GitLab 12.1 and earlier should use the command `gitlab-rake gitlab:back
 
 #### Excluding specific directories from the backup
 
-You can choose what should be exempt from the backup by adding the environment
-variable `SKIP`. The available options are:
+You can exclude specific directories from the backup by adding the environment variable `SKIP`, whose values are a comma-separated list of the following options:
 
 - `db` (database)
 - `uploads` (attachments)
-- `repositories` (Git repositories data)
 - `builds` (CI job output logs)
 - `artifacts` (CI job artifacts)
 - `lfs` (LFS objects)
 - `registry` (Container Registry images)
 - `pages` (Pages content)
+- `repositories` (Git repositories data)  
 
-Use a comma to specify several options at the same time:
+All wikis will be backed up as part of the `repositories` group. Non-existent wikis will be skipped during a backup.
+  
+NOTE: **Note:**
+When [backing up and restoring Helm Charts](https://docs.gitlab.com/charts/architecture/backup-restore.html), there is an additional option `packages`, which refers to any packages managed by the GitLab [package registry](../user/packages/package_registry/index.md).   
+For more information see [command line arguments](https://docs.gitlab.com/charts/architecture/backup-restore.html#command-line-arguments).
 
 All wikis are backed up as part of the `repositories` group. Non-existent
 wikis are skipped during a backup.