Added `chown git` to the backup tar to prevent permission denied errors.

What does this MR do?

Added text comment and additional chown command to the restore instructions if the backup tarfile is not already owned. If the tarfile is owned by root, permission failures occur on untar.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides