Merge branch 'docs-import-links' into 'master'

Linking to backup doc from migration doc, for self-hosted to self-hosted migration

Closes #56339

See merge request gitlab-org/gitlab-ce!24592

doc/user/project/import/index.md

@@ -25,3 +25,10 @@ but issues and merge requests can't be imported.
 
 If you want to retain all metadata like issues and merge requests, you can use
 the [import/export feature](../settings/import_export.md).
+
+## Migrating between two self-hosted GitLab instances
+
+The best method for migrating a project from one GitLab instance to another,
+perhaps from an old server to a new server for example, is to
+[back up the project](../../../raketasks/backup_restore.md),
+then restore it on the new server.