Changed port to reflect MySQL -> Postgres change

Updated the default port to reflect MySQL to Postgres change (port 3306 to 5432)

roles/news/templates/var_www_selfoss_config.ini.j2

 db_database={{selfoss_db_database}}
 db_username={{selfoss_db_username}}
 db_password={{selfoss_db_password}}
-db_port=3306
+db_port=5432
 db_prefix=
 logger_level=DEBUG
 items_perpage=50