Fixed code highlighting

| Q   | A
| --- | ---
| Doc fix? | yes
| New docs? | no
| Applies to | all
| Fixed tickets | -

 > Double quoted strings are the only scalar style capable of expressing arbitrary strings, by using “\” escape sequences.
 > - http://yaml.org/spec/1.1/#id904245

`\w` is an invalid escape sequence in Yaml, causing the Yaml highlighter to fail.