fix: backup dereference (for docker)

[FeneralGeldmarschall]

Description

Added the -h flag to the tar backup command so it follows symlinks, which is relevant for docker containers as otherwise only the symlink to the serverfiles is backed up.

Fixes #4746

Type of change

• Bug fix (a change which fixes an issue).
• New feature (a change which adds functionality).
• New Server (new server added).
• Refactor (restructures existing code).
• Comment update (typo, spelling, explanation, examples, etc).

Checklist

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• This pull request links to an issue.
• This pull request uses the develop branch as its base.
• This pull request subject follows the Conventional Commits standard.
• This code follows the style guidelines of this project.
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• I have checked if documentation needs updating.

Documentation

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• User docs: https://github.com/GameServerManagers/LinuxGSM-Docs
• Dev docs: https://github.com/GameServerManagers/LinuxGSM-Dev-Docs

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