deps(upgrade): bump org.testcontainers:testcontainers

Bumps [org.testcontainers:testcontainers](https://github.com/testcontainers/testcontainers-java) from 1.20.6 to 1.21.3.
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.20.6...1.21.3)

---
updated-dependencies:
- dependency-name: org.testcontainers:testcontainers
  dependency-version: 1.21.3
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

build.gradle.kts

@@ -106,7 +106,7 @@ dependencies {
     testImplementation("org.mockito:mockito-core:4.11.0")
     testImplementation("org.mockito:mockito-inline:4.11.0")
     testImplementation("org.mockito:mockito-junit-jupiter:4.11.0")
-    testImplementation("org.testcontainers:testcontainers:1.20.6")
+    testImplementation("org.testcontainers:testcontainers:1.21.3")
     testImplementation("org.assertj:assertj-core:3.27.3")
 }