build(deps): Bump org.postgresql:postgresql

Bumps [org.postgresql:postgresql](https://github.com/pgjdbc/pgjdbc) from 42.6.0 to 42.7.3.
- [Release notes](https://github.com/pgjdbc/pgjdbc/releases)
- [Changelog](https://github.com/pgjdbc/pgjdbc/blob/master/CHANGELOG.md)
- [Commits](pgjdbc/pgjdbc@REL42.6.0...REL42.7.3)

---
updated-dependencies:
- dependency-name: org.postgresql:postgresql
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

promotion-notifier-backend/pn-user-service/build.gradle

@@ -49,7 +49,7 @@ dependencies {
     implementation 'org.springframework.boot:spring-boot-starter-web'
     implementation group: 'org.springframework.boot', name: 'spring-boot-starter-data-jpa'
     implementation group: 'org.springframework.boot', name: 'spring-boot-starter-validation'
-    implementation group: 'org.postgresql', name: 'postgresql', version: '42.6.0'
+    implementation group: 'org.postgresql', name: 'postgresql', version: '42.7.3'
     implementation 'org.springframework.boot:spring-boot-starter-actuator'
     implementation "io.micrometer:micrometer-registry-prometheus"