Test only - bump to Postgres 17 for PostgresReadOnlyDatabaseTest

Author: rbygrave

ebean-test/src/test/java/org/tests/readonly/PostgresReadOnlyDatabaseTest.java

@@ -81,7 +81,7 @@ void transactionalOnlyContainingQueries() {
   }
 
   private static Database setupReadOnlyDatabase() {
-    PostgresContainer.builder("15")
+    PostgresContainer.builder("17")
       .dbName("readonly_test")
       .build()
       .start();