chore(gradle): bump org.postgresql:postgresql from 42.7.1 to 42.7.3

Bumps [org.postgresql:postgresql](https://github.com/pgjdbc/pgjdbc) from 42.7.1 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@REL42.7.1...REL42.7.3)

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

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

authentication/example-providers/sql-username-password/build.gradle

@@ -3,7 +3,7 @@ configurations {
     pwGen
 }
 dependencies {
-    implementation('org.postgresql:postgresql:42.7.1') {
+    implementation('org.postgresql:postgresql:42.7.3') {
         because 'Postgres driver to connect to a running DB to query for user information'
     }
     implementation('org.mindrot:jbcrypt:0.4') {