Bump org.testcontainers:testcontainers-bom from 1.21.2 to 1.21.3 (#3114)

Bumps [org.testcontainers:testcontainers-bom](https://github.com/testcontainers/testcontainers-java) from 1.21.2 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@1.21.2...1.21.3)

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

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

Author: dependabot[bot]

build.gradle

@@ -56,7 +56,7 @@ ext {
 	springDataVersion = '2025.1.0-SNAPSHOT'
 	springRetryVersion = '2.0.12'
 	springVersion = '7.0.0-SNAPSHOT'
-	testcontainersVersion = '1.21.2'
+	testcontainersVersion = '1.21.3'
 
 	javaProjects = subprojects - project(':spring-amqp-bom')
 }