build(deps): bump org.postgresql:postgresql in /backend

Bumps [org.postgresql:postgresql](https://github.com/pgjdbc/pgjdbc) from 42.6.0 to 42.7.2.
- [Release notes](https://github.com/pgjdbc/pgjdbc/releases)
- [Changelog](https://github.com/pgjdbc/pgjdbc/blob/master/CHANGELOG.md)
- [Commits](https://github.com/pgjdbc/pgjdbc/commits)

---
updated-dependencies:
- dependency-name: org.postgresql:postgresql
  dependency-type: direct:production
...

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

backend/pom.xml

@@ -27,7 +27,7 @@
         <spring.ws.version>6.0.11</spring.ws.version>
 
         <!-- PERSISTENCE -->
-        <postgresql.version>42.6.0</postgresql.version>
+        <postgresql.version>42.7.2</postgresql.version>
         <hibernate-spatial.version>6.1.7.Final</hibernate-spatial.version>
         <hypersistence-utils-hibernate.version>3.5.1</hypersistence-utils-hibernate.version>