[CVE-2025-61770] bump rack to 2.2.19

[meghanmurphy1]

Relates https://github.com/elastic/search-team/issues/11475

Bump Rack to 2.2.19 because of this CVE

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Pre-Review Checklist

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Changes Requiring Extra Attention

• Security-related changes (encryption, TLS, SSRF, etc)
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