404s on Help documentation

Repro:

1. Go to: https://gitlab.com/help
2. Click on "Install"
3. Click on "Installation"
4. Click on "contributing guide"

Expected Result: Navigate user to page regarding contributing Actual Result: 404 Error

Note: On the same Installation page, user gets a 404 also when clicking on: "omniauth integration document"

BUILD: 7.7.2/a792f98b