Don't say "K&R style" in coding conventions

Summary: We technically don't use K&R. These documents and the rest of the codebase are full of examples of the correct style, which should be unambiguous to a reasonable reader.

Test Plan: reading

Reviewers: staticshock, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D11255