build(deps): bump testcontainers from 1.19.3 to 1.21.4 (#37)

Bumps `testcontainers` from 1.19.3 to 1.21.4.

Updates `org.testcontainers:mongodb` from 1.19.3 to 1.21.4
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.19.3...1.21.4)

Updates `org.testcontainers:postgresql` from 1.19.3 to 1.21.4
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.19.3...1.21.4)

---
updated-dependencies:
- dependency-name: org.testcontainers:mongodb
  dependency-version: 1.21.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.testcontainers:postgresql
  dependency-version: 1.21.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -18,7 +18,7 @@ logback = "1.5.32"
 
 # Test
 kotest = "5.8.0"
-testcontainers = "1.19.3"
+testcontainers = "1.21.4"
 kotest-extensions-testcontainers = "2.0.2"
 mockk = "1.13.9"
 flyway = "11.10.2"