Bump org.testcontainers:testcontainers from 1.19.7 to 1.21.3 (#666)

Bumps [org.testcontainers:testcontainers](https://github.com/testcontainers/testcontainers-java) from 1.19.7 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@1.19.7...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
...

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

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -35,7 +35,7 @@ truth = { group = "com.google.truth", name = "truth", version = "1.4.2" }
 truth-proto-extension = { group = "com.google.truth.extensions", name = "truth-proto-extension", version = "1.4.2" }
 okhttp = { group = "com.squareup.okhttp", name = "okhttp", version = "2.7.5" }
 javax-annotation-api = { group = "javax.annotation", name = "javax.annotation-api", version = "1.3.2" }
-testcontainers = { group = "org.testcontainers", name = "testcontainers", version = "1.19.7" }
+testcontainers = { group = "org.testcontainers", name = "testcontainers", version = "1.21.3" }
 slf4j-simple = { group = "org.slf4j", name = "slf4j-simple", version = "2.0.12" }
 gradle-test-kit = { group = "org.gradle", name = "gradle-test-kit", version = "6.1" }
 gradle-tooling-api = { group = "org.gradle", name = "gradle-tooling-api", version = "8.6" }