Bump org.testcontainers:testcontainers-bom from 1.20.2 to 1.20.3 (#473)

Bumps [org.testcontainers:testcontainers-bom](https://github.com/testcontainers/testcontainers-java) from 1.20.2 to 1.20.3.
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.20.2...1.20.3)

---
updated-dependencies:
- dependency-name: org.testcontainers:testcontainers-bom
  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>

gradle/libs.versions.toml

@@ -4,7 +4,7 @@ detekt = "1.23.6"
 commons-lang3 = "3.17.0"
 slf4j = "1.7.36" # to be compatible with Spring Boot 2.7.X
 assertj = "3.26.3"
-testcontainers = "1.20.2"
+testcontainers = "1.20.3"
 junit = "5.11.2"
 mockito = "5.14.1"
 forbiddenapis = "3.8"