CodeMirror uses the .cm-comment class to indicated inline and fenced code

blocks, which our reviews CSS displays in italics. This change overrides that

class when inside a CodeMirror to not show italics.

Wrote a comment with inline and fenced code blocks. Saw that the text was no

  longer italicized in the editor.
Published a review with a code block containing a comment. Saw that comment

  was displayed in italics.