Update SqlService API documentation (#479)
Update SqlService API documentation (#479)

* Update SqlService API documentation

- Removed the warning about the BETA status
- Similar to Java client, simplified the API doc as most of the
things we mention here is already mentioned in the actual
SQL documentation
- Add a warning about enabling Jet and adding `hazelcast-sql`
to the member's classpath
- And other minor updates.

* typo fix
hazelcast/hazelcast-python-client,hazelcast/hazelcast-python-client