chore: Fix transitive vulnerability in jackson

[Mahoney]

Set the minimum version to 2.15.0. Version 2.14.2 brought in
transitively by com.auth0:[email protected] has CWE-400.

A gradle constraint does not fix the version, just sets a minimum
version: https://www.linen.dev/s/gradle-community/t/22694678/hi-snyk-has-revealed-that-some-deeply-nested-transitive-depe#e46476e5-70e1-49a7-a72f-fa5453374e42

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