Update zuul-changes.py doc to match usage
Update zuul-changes.py doc to match usage

zuul-changes.py does not accept --review-host param
since 574ec76a6085b13fb1f02697e68baea7cc0bb63b

It's usage output is:
usage: zuul-changes.py [-h] url pipeline_name

Correct the docs to match.

Change-Id: Iab8158f73f6b1611d088377e36a7d076907bf8f6

gooddata/zuul,gooddata/zuul,wikimedia/integration-zuul,wikimedia/integration-zuul,wikimedia/integration-zuul,gooddata/zuul,gooddata/zuul,wikimedia/integration-zuul,gooddata/zuul