[Aikido] Fix security issue in json via minor version upgrade from 2.19.4 to 2.19.7 in test

[aikido-autofix]

Upgrade json gem to fix heap buffer overflow in generation and use-after-free in parsing caused by integer overflow and concurrent string mutation.

✅ 2 CVEs resolved by this upgrade

This PR will resolve the following CVEs:

Issue	Severity	Description
AIKIDO-2026-10977	LOW	[json] A heap buffer overflow vulnerability exists in the native generator when computing output buffer capacity for repeated indent/spacing strings, potentially causing memory corruption. Additionally, an unchecked depth option can cause denial of service through excessive nesting work.
AIKIDO-2026-10978	LOW	[json] A use-after-free vulnerability in JSON parsing allows concurrent mutation of the source string during parsing through Ruby-level hooks, potentially causing memory corruption and parsed value divergence. The patch freezes or copies the source buffer to prevent modification during parsing.

🔗 Related Tasks

• https://aikido.atlassian.net/browse/AIK-14296

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[aikido-autofix]

Closed by Aikido: a new AutoFix has been created → #294