Test merge editor: highlight color on conflict selection a bit subtle

[andreamah]

Testing #158819

Especially when highlighting a conflict that uses a dotted line, it can be tricky to tell whether something is highlighted. Especially with high-contrast themes, I'd prefer a more stark difference in colour when it's supposed to be highlighted.

[daviddossett]

To clarify, is this about word highlight (background colors on changed chars/words) or the entire conflict (yellow borders)? Here's what the entire conflict selection now looks like after some recent changes:

[andreamah]

@daviddossett it was mostly about the highlight of the entire conflict. When your cursor is in a conflict, it seems to turn the border darker/lighter, but only by a little bit. Ideally, the border color change here would be more drastic.

[daviddossett]

Got it, thank! Should be fixed via #159208 and #159199