Fix email signup steps features test
Fix email signup steps features test

This broke due to the disappearance of the catch all detailed
guide routes at the root. Now sending client to a functioning
url in Whitehall, as I do not know the url of the email sign up
page.

FIXME: replace mock_client url stub with email sign up page url

alphagov/whitehall,alphagov/whitehall,alphagov/whitehall,alphagov/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,ggoral/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,YOTOV-LIMITED/whitehall,YOTOV-LIMITED/whitehall,ggoral/whitehall