build(deps): bump testcontainers from 1.21.3 to 1.21.4

Bumps `testcontainers` from 1.21.3 to 1.21.4.

Updates `org.testcontainers:testcontainers` from 1.21.3 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@1.21.3...1.21.4)

Updates `org.testcontainers:postgresql` from 1.21.3 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@1.21.3...1.21.4)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -39,7 +39,7 @@ detekt = "1.23.8"
 xmlunit = "2.11.0"
 kotest = "6.0.7"
 reaktive = "2.2.0"
-testcontainers = "1.21.3"
+testcontainers = "1.21.4"
 keycloak = "26.0.7"
 arrow = "2.2.0"