Update cx_Oracle to the latest version - which doesn't need Instant Client.

[cjbj]

https://github.com/oracle-samples/oracle-functions-samples/blob/master/samples/oci-adb-client-runsql-python/func.py needs to be updated to the latest cx_Oracle driver, which is now called python-oracledb. This no longer needs Oracle Instant Client. See the release announcement.