Fix update iso seg example
Fix update iso seg example

The CC docs [1] says the request should be a PATCH, not a PUT. I've confirmed that it is a PATCH request

1. http://v3-apidocs.cloudfoundry.org/version/3.12.0/index.html#update-an-isolation-segment
cf-routing/docs-cf-admin,cloudfoundry/docs-cf-admin