build(deps): bump joda-time:joda-time from 2.11.2 to 2.12.6 in /backend

Bumps [joda-time:joda-time](https://github.com/JodaOrg/joda-time) from 2.11.2 to 2.12.6.
- [Release notes](https://github.com/JodaOrg/joda-time/releases)
- [Changelog](https://github.com/JodaOrg/joda-time/blob/main/RELEASE-NOTES.txt)
- [Commits](JodaOrg/joda-time@v2.11.2...v2.12.6)

---
updated-dependencies:
- dependency-name: joda-time:joda-time
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/pom.xml

@@ -63,7 +63,7 @@
         <dependency>
             <groupId>joda-time</groupId>
             <artifactId>joda-time</artifactId>
-            <version>2.11.2</version>
+            <version>2.12.6</version>
         </dependency>
         <dependency>
             <groupId>net.sf.ehcache</groupId>