Bump org.assertj:assertj-core in /testing/testcontainers/java

Bumps [org.assertj:assertj-core](https://github.com/assertj/assertj) from 3.26.0 to 3.26.3.
- [Release notes](https://github.com/assertj/assertj/releases)
- [Commits](assertj/assertj@assertj-build-3.26.0...assertj-build-3.26.3)

---
updated-dependencies:
- dependency-name: org.assertj:assertj-core
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

testing/testcontainers/java/build.gradle

@@ -25,7 +25,7 @@ dependencies {
     implementation 'org.slf4j:slf4j-api:2.0.13'
     implementation 'org.slf4j:slf4j-simple:2.0.13'
     testImplementation 'junit:junit:4.13.2'
-    testImplementation "org.assertj:assertj-core:3.26.0"
+    testImplementation "org.assertj:assertj-core:3.26.3"
     testImplementation 'org.testcontainers:testcontainers:1.19.8'
     testImplementation 'org.testcontainers:cratedb:1.19.8'
     testImplementation 'org.testcontainers:postgresql:1.19.8'