Revert "Compress requests from the Conduit client to Phabricator"

Summary:
This reverts commit 7e25288f496887a78d1ba4a54753c2cca09a6336. See T13507 for discussion, shortly.

This needs to be switched to capability detection because some server configurations can not actually accept these requests.

Test Plan: Straight revert.

Differential Revision: https://secure.phabricator.com/D21076