Bump org.testcontainers:testcontainers from 1.19.3 to 1.21.3

Bumps [org.testcontainers:testcontainers](https://github.com/testcontainers/testcontainers-java) from 1.19.3 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@1.19.3...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

@@ -74,8 +74,8 @@ dependencies {
     testImplementation 'com.h2database:h2:2.3.232'
 
     // Additional test dependencies for improved testing
-    testImplementation 'org.testcontainers:testcontainers:1.19.3'
-    testImplementation 'org.testcontainers:mariadb:1.19.3'
+    testImplementation 'org.testcontainers:testcontainers:1.21.3'
+    testImplementation 'org.testcontainers:mariadb:1.21.3'
     testImplementation 'com.github.tomakehurst:wiremock:3.0.1'
     testImplementation 'com.tngtech.archunit:archunit-junit5:1.2.0'
     testImplementation 'org.assertj:assertj-core:3.24.2'