Summary: See PHI1268. We currently do some weird width handling when rendering Diffusion readmes in a document directory view. I think this came from D12330, which used `PHUIDocumentViewPro` to change the font, but we later reverted the font and were left with the `DocumentView`. Other changes after that modified `DocumentView` to have fixed-width behavior, but it doesn't make much sense here since the content panel is clearly rendered full-width. Today, the `DocumentView` is a more structural element with methods like `setCurtain()`. Just get rid of it to simplify things, at least as a first step. Test Plan: Before: {F6463493} After: {F6463492} Reviewers: amckinley Reviewed By: amckinley Differential Revision: https://secure.phabricator.com/D20536