fix a typo in documentation
fix a typo in documentation

Change-Id: I0492ae1d50493585ead919904d6d9502b7738266

matthewoliver/swift,matthewoliver/swift,tipabu/swift,matthewoliver/swift,tipabu/swift,smerritt/swift,smerritt/swift,openstack/swift,smerritt/swift,tipabu/swift,swiftstack/swift,swiftstack/swift,smerritt/swift,openstack/swift,swiftstack/swift,openstack/swift,openstack/swift,tipabu/swift,matthewoliver/swift