Make collapsed file diffs visually more prominent

Problem to solve

I often find myself scrolling past collapsed file diffs when reviewing MRs, probably because my brain recognise the notice replacing the content as white space, instead of something of importance.

Further details

This may be emphasised because I use a dark theme for diffs, but the notice about the collapsed diff has a light background.

Proposal

Apply a styling similar to the code to the notice. Or do something else to make the notice stand out and alert me that there's something that needs my attention.

What does success look like, and how can we measure that?

Success is when I remember to expand the collapsed diffs as part of my code review. As the diffs are fetched via XHR, I bet it's quite easy to measure whether I remember to expand the diffs.