Upgrade PostgreSQL JDBC 42.3.5 -> 42.3.6 (#214)

See:
- https://jdbc.postgresql.org/documentation/changelog.html
- pgjdbc/pgjdbc@REL42.3.5...REL42.3.6

pom.xml

@@ -106,7 +106,7 @@
         <version.maven-plugin-tools>3.6.0</version.maven-plugin-tools>
         <version.mockito>4.5.1</version.mockito>
         <version.nullaway>0.9.7</version.nullaway>
-        <version.postgresql>42.3.5</version.postgresql>
+        <version.postgresql>42.3.6</version.postgresql>
         <version.surefire>2.22.2</version.surefire>
     </properties>