Hmm... When adding the %actions-header extend, I left rules that differed from the extend rather than check whether or not they were all actually necessary.  It doesn't look like it is necessary here in _assets.scss so I've gone ahead and removed it. 

I started playing with updating staticpages, unit, and outline styling to also use the extend, but they differ in enough ways that this is worth tackling in a separate PR for now.