Re-generate Coderay syntax highlighting styles

Coderay 1.0+ now uses more descriptive class names.
We use the default (alpha) styles:

`coderay stylesheet > app/assets/stylesheets/coderay.css`

Hotfix # 17114

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Merge pull request #2321 from opf/hotfix/17114-syntax-highlighting-missing-styles