build(deps): bump testcontainersVersion from 1.20.4 to 1.21.0 (#175)

Bumps `testcontainersVersion` from 1.20.4 to 1.21.0.

Updates `org.testcontainers:junit-jupiter` from 1.20.4 to 1.21.0
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.20.4...1.21.0)

Updates `org.testcontainers:kafka` from 1.20.4 to 1.21.0
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.20.4...1.21.0)

---
updated-dependencies:
- dependency-name: org.testcontainers:junit-jupiter
  dependency-version: 1.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.testcontainers:kafka
  dependency-version: 1.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

build.gradle

@@ -47,7 +47,7 @@ ext {
     junit5Version = "5.12.2"
     kafkaVersion = "2.0.1"
     log4jVersion = "2.24.3"
-    testcontainersVersion = "1.20.4"
+    testcontainersVersion = "1.21.0"
 }
 
 distributions {