Default remarkup code blocks to plain text, not PHP
Summary:
Ref T6823. If we have no language information for a block, render it without syntax highlighting instead of with PHP syntax highlighting.
Thinking is to try this, see who notices/complains, and then pursue more tailored defaults if they seem worthwhile.
Test Plan: Wrote a code block with text in it, saw no default highlighting.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T6823
Differential Revision: https://secure.phabricator.com/D11091