Don't escape quotation marks when printing the monospaced CSS rule

Summary:
Fixes T7888. This is currently safe, but double quotes are incorrectly escaped.

To keep them unescaped, we have to punch through PhutilSafeHTML a bit. Since the allowable characters are strictly filtered this is still safe in practice, just not as theoretically-safe.

Test Plan: Set font to 32px "impact" (with quotes), saw impact font.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T7888

Differential Revision: https://secure.phabricator.com/D12506