To improve wrapping behavior of rendered README files, don't use "PHUIDocumentView" in Diffusion
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