Bump postgresql from 42.2.18 to 42.2.20 in /modules/spock

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/REL42.2.20/CHANGELOG.md)
- [Commits](pgjdbc/pgjdbc@REL42.2.18...REL42.2.20)

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

Author: dependabot[bot]

modules/spock/build.gradle

@@ -15,7 +15,7 @@ dependencies {
     testImplementation 'com.zaxxer:HikariCP:4.0.3'
     testImplementation 'org.apache.httpcomponents:httpclient:4.5.13'
 
-    testRuntimeOnly 'org.postgresql:postgresql:42.2.18'
+    testRuntimeOnly 'org.postgresql:postgresql:42.2.20'
     testRuntimeOnly 'mysql:mysql-connector-java:8.0.25'
 
     testCompileClasspath 'org.jetbrains:annotations:21.0.1'