Correct documentation for Oracle XStream

Documentation section Connectors > Oracle > XStreams support

1. XStream user needs to be able to select any table for the connector to work, i.e. need to add

   GRANT SELECT ANY TABLE TO c##dbzuser CONTAINER=ALL;

1. The example configuration for the XStream Outbound Server is misleading: 

   schemas(1) := 'debezium';

    should be changed to 

   schemas(1) := NULL;