chore(deps): bump jackson 2.21.1 → 2.21.4 (hygiene, activemq-6.1.x-TT.x)

[jeanouii]

Summary

Hygiene bump only — Jackson 2.21.1 → 2.21.4 (latest 2.21 patch on Maven Central).

This is not a CVE patch. CVE-2026-50193 (jackson-databind InternalNodeMapper StackOverflowError) was audited as NOT AFFECTED on ActiveMQ across every TT-shipped branch. The broker does not call InternalNodeMapper.nodeToString / toPrettyString / JsonNode.toString() anywhere; Jolokia uses json-simple (1.x) or jolokia-json (2.x), not Jackson.

See docs/security-audits/2026/CVE-2026-50193.md in tomitribe/cve for the full audit (L1-L4, bytecode strings sweep, per-vector trace).

Why bump anyway

• Defence in depth (any future code path that introduces a Jackson use case inherits the fixed code).
• NexusIQ / SBOM scans report a clean Jackson version on the shipped distribution.
• Trivial: 1-line property change, no API delta within the 2.21.x line.

Test plan

• Jenkins stable build green
• Jenkins PR-manual build green
• Flaky-compare matrix (stable vs PR) shows no patch-induced regressions

Branch

Base: activemq-6.1.x-TT.x. Latest released TT on this branch when the PR was opened: activemq-6.1.9-TT.7.

Audit trail: https://github.com/tomitribe/cve/blob/main/docs/security-audits/2026/CVE-2026-50193.md