Update dependency org.postgresql:postgresql to v42.2.20

Author: renovate-bot

backend/pom.xml

@@ -19,7 +19,7 @@
 
 		<!-- backend dependencies -->
 		<rest-assured.version>4.3.3</rest-assured.version>
-		<postgresql.version>42.2.19</postgresql.version>
+		<postgresql.version>42.2.20</postgresql.version>
 		<groovy.version>3.0.8</groovy.version>
 	</properties>