R1:6b69bc3fbbb1

Delete all "force chunking" file upload code

Summary: Ref T7149. This was just to make testing easier, but chunking substantially works now.

Test Plan: `grep`

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7149

Differential Revision: https://secure.phabricator.com/D12076