[backend] Update dependency org.postgresql:postgresql to v42.7.4

Co-authored-by: Romuald Lemesle <romuald.lemesle@filigran.io>

pom.xml

@@ -68,7 +68,7 @@
             <groupId>org.postgresql</groupId>
             <artifactId>postgresql</artifactId>
             <scope>runtime</scope>
-            <version>42.6.2</version>
+            <version>42.7.4</version>
         </dependency>
     </dependencies>