fix(ruler): Return StatusBadRequest on multiple org IDs (backport k257)

[loki-gh-app]

Backport f7e47f0 from #17850

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What this PR does / why we need it:
This pull request provides a small fix to return BadRequest as the status code when a client if sending multiple org ids to the ruler API.

Which issue(s) this PR fixes:
Fixes #grafana/loki-private/issues/1335

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
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