Bump postgresql from 42.2.18 to 42.2.20 in /examples

Bumps [postgresql](https://github.com/pgjdbc/pgjdbc) from 42.2.18 to 42.2.20.
- [Release notes](https://github.com/pgjdbc/pgjdbc/releases)
- [Changelog](https://github.com/pgjdbc/pgjdbc/blob/master/CHANGELOG.md)
- [Commits](pgjdbc/pgjdbc@REL42.2.18...REL42.2.20)

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

Author: dependabot[bot]

examples/linked-container/build.gradle

@@ -9,7 +9,7 @@ dependencies {
     compileOnly 'org.slf4j:slf4j-api:1.7.30'
     implementation 'com.squareup.okhttp3:okhttp:4.9.0'
     implementation 'org.json:json:20210307'
-    testImplementation 'org.postgresql:postgresql:42.2.18'
+    testImplementation 'org.postgresql:postgresql:42.2.20'
     testImplementation 'ch.qos.logback:logback-classic:1.2.3'
     testImplementation 'org.testcontainers:postgresql'
 }