bug21691: typo in python API tutorial

tests added    : no
tests run      : no
performance    : no change
release note   : none, it's just a typo :-)

Change-Id: Ibb05f60c35437219ed7fe24af5a59a2f7e13e1b8
Reviewed-on: https://gerrit.franz.com:9080/2973
Reviewed-by: Ahmon Dancy <dancy@franz.com>
Reviewed-by: John O'Rourke <jor@franz.com>
Tested-by: Kevin Layer <layer@franz.com>