fixed the multi-line issue for criterion prompt, criterion option text,

Fixed the multi-line issue for criterion prompt, criterion option text, peer assessment feedback and self assessment feedback. tnl-814
NIT: please 1) add line break between this nested rule and its Sass parent and 2) use the [class name suggestions from above](https://github.com/edx/edx-ora2/pull/636/files#r21065755)