Bump org.postgresql:postgresql in /opendj-server-legacy

Bumps [org.postgresql:postgresql](https://github.com/pgjdbc/pgjdbc) from 42.7.8 to 42.7.11.
- [Release notes](https://github.com/pgjdbc/pgjdbc/releases)
- [Changelog](https://github.com/pgjdbc/pgjdbc/blob/master/CHANGELOG.md)
- [Commits](https://github.com/pgjdbc/pgjdbc/compare/REL42.7.8...REL42.7.11)

---
updated-dependencies:
- dependency-name: org.postgresql:postgresql
  dependency-version: 42.7.11
  dependency-type: direct:production
...

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