Bump postgresql from 42.2.12 to 42.2.20 (#136)

Bumps [postgresql](https://github.com/pgjdbc/pgjdbc) from 42.2.12 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@REL42.2.12...REL42.2.20)

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pom.xml

@@ -135,7 +135,7 @@
 		<dependency>
 			<groupId>org.postgresql</groupId>
 			<artifactId>postgresql</artifactId>
-			<version>42.2.12</version>
+			<version>42.2.20</version>
 		</dependency>
 		<dependency>
 			<groupId>com.typesafe.slick</groupId>