Bump postgresql from 42.3.3 to 42.3.8 in /nakadi-producer-loadtest

Bumps [postgresql](https://github.com/pgjdbc/pgjdbc) from 42.3.3 to 42.3.8.
- [Release notes](https://github.com/pgjdbc/pgjdbc/releases)
- [Changelog](https://github.com/pgjdbc/pgjdbc/blob/master/CHANGELOG.md)
- [Commits](pgjdbc/pgjdbc@REL42.3.3...REL42.3.8)

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

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

nakadi-producer-loadtest/pom.xml

@@ -31,7 +31,7 @@
         <dependency>
             <groupId>org.postgresql</groupId>
             <artifactId>postgresql</artifactId>
-            <version>42.3.3</version>
+            <version>42.3.8</version>
         </dependency>
         <dependency>
             <groupId>org.zalando.stups</groupId>