Add read permission instructions for migration archive (#56996)

Co-authored-by: Copilot <[email protected]>

Author: megamanics

content/migrations/using-ghe-migrator/migrating-data-to-github-enterprise-server.md

@@ -35,6 +35,12 @@ shortTitle: Migrate data
 
 {% data reusables.enterprise_installation.ssh-into-target-instance %}
 
+1. Ensure the migration archive has sufficient read permissions.
+
+   ```shell
+   chmod 644 /home/admin/MIGRATION-GUID.tar.gz
+   ```
+
 1. Use the `ghe-migrator prepare` command to prepare the archive for import on the target instance and generate a new Migration GUID for you to use in subsequent steps:
 
    ```shell