Inconsistency between Header and Sidebar links

[loujar]

As observed on the Deploy Overview page, the links on the sidebar are different than the links in their associated header elements:

In this case, the header element link resolves to the correct page while the sidebar link is broken:

header link: https://docs.sourcegraph.com/admin/deploy/machine-images
sidebar link: https://docs.sourcegraph.com/admin/machine-images/index.md (broken)

[loujar]

@unknwon as discussed in slack