Update Pages getting started guide to point to correct help page

Summary

On the GitLab.com new project page the link to Pages getting started guide links to a page that has moved.

Steps to reproduce

• Go to: https://gitlab.com/projects/new
• Click on: Pages getting started guide

What is the current bug behavior?

• Page displays 'This document was moved to another location'.

What is the expected correct behavior?

Link should have gone directly to user/project/pages/index.md#getting-started

OR

https://gitlab.com/help/user/project/pages/getting_started/fork_sample_project.md

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com (self-hosted not tested, but will be applicable).

Possible fixes

https://gitlab.com/gitlab-org/gitlab/blob/master/app/views/projects/new.html.haml#L21