Update PostgreSQL Docker image to 12.20

Author: nakamura-to

gradle.properties

@@ -19,5 +19,5 @@ h2.url=jdbc:h2:mem:test;DB_CLOSE_DELAY=-1
 mysql.url=jdbc:tc:mysql:5.7:///test?TC_DAEMON=true&allowMultiQueries=true
 mysql8.url=jdbc:tc:mysql:8.0.36:///test?TC_MY_CNF=mysql_conf_override&TC_DAEMON=true&allowMultiQueries=true
 oracle.url=jdbc:tc:oracle:21-slim-faststart:thin:@test?TC_DAEMON=true
-postgresql.url=jdbc:tc:postgresql:10.16:///test?TC_DAEMON=true
+postgresql.url=jdbc:tc:postgresql:12.20:///test?TC_DAEMON=true
 sqlserver.url=jdbc:tc:sqlserver:2019-CU12-ubuntu-20.04:///test?TC_DAEMON=true