docs: sandbox fix for quickstart (backport release-3.1.x)

[loki-gh-app]

Backport 16acdf6 from #15358

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What this PR does / why we need it:
This is a quick fix to the changes added to the getting started demo:

• Added setup script to upgrade docker-compose to the latest version in sandbox.
• Removed out-of-date command

https://killercoda.com/grafana-dev-testing/course/loki/loki-quickstart

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR