chore(deps): bump org.junit:junit-bom from 5.11.2 to 5.11.3 in /backend

Bumps [org.junit:junit-bom](https://github.com/junit-team/junit5) from 5.11.2 to 5.11.3.
- [Release notes](https://github.com/junit-team/junit5/releases)
- [Commits](junit-team/junit5@r5.11.2...r5.11.3)

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

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

backend/build.gradle

@@ -160,7 +160,7 @@ subprojects {
 
         implementation "com.rometools:rome-opml:2.1.0"
 
-        testImplementation(platform('org.junit:junit-bom:5.11.2'))
+        testImplementation(platform('org.junit:junit-bom:5.11.3'))
         testImplementation('org.junit.jupiter:junit-jupiter')
     }
 }