R1:5897b4a11617

Remove "preview.viewport-meta-tag" config

Summary: This is obsolete with the 'device' => true stuff, which is more granular and generally better.

Test Plan: grep

Reviewers: btrahan, codeblock

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4309