Fix help link for Cloud.gov login screen

[cand-des]

The Need help? link under the cloud.gov login screen points to a 404 page on the Cloud.gov site

Notes

• Screenshot of link highlighted:

Acceptance Criteria

• Link correctly navigates to its intended destination for support or documentation

[sknep]

@soutenniza Do you know where this page is generated? It's not actually in the marketing site...

[pburkholder]

I've opened a PR for this:cloud-gov/deploy-shibboleth#80