chore(deps): bump org.testcontainers:testcontainers-bom from 1.19.7 to 1.21.4 - #21

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11d5960a326750d5838078e36cf38b85af677262, actions/setup-java@cf277c60eb25467037889841efdb72551f06f6c3, dorny/test-reporter@6c357194179c694acfcad2100dbf27c5b9b0d5e0. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/