R1:cfd9fa7f559f

Add an explicit "max-width" to PHUIDocumentPro pages to force large tables to scroll

Summary:
Ref T13202. See <https://discourse.phabricator-community.org/t/phriction-page-controls-lost-after-creating-very-wide-table/1961>.

If you put a very wide table in the markup for a new-layout Phriction page, it can push the actions element off screen to the right.

Tables already get a scrollbar if encouraged strongly enough; add a `max-width` to encourage them.

Test Plan:
- Viewed pages with a large wrappable…