Let width of horizontal dividers match new dropdown hover style

As noted by @annabeldunstone in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13106#note_36333641, dividers for the new dropdown style should have the same width as the hover background. This was caused by #28921 (moved) and will be resolved along with it.

@cperessini @pedroms Is this how it should look like?

changed milestone to %9.5

changed title from Let width of horizontal dividers match hover style to Let width of horizontal dividers match new dropdown hover style

mentioned in merge request !13106 (merged)

@winh yup, looks good

added UX ready label

assigned to @pedroms

Great! I'll review the other MRs are just changing the hover style then

mentioned in merge request !13276 (merged)

@cperessini @pedroms I just had a moment of uncertainty could you confirm which of the following is correct?

full width:

1px margin:

From @pedroms in slack:

I think the line has the same color (or approx.) of the dropdown border, so I’d say completely full-width

@winh looks like the first one is the one to go with!

To be honest I'm not a huge fan of the 1px white border on either side of the hover item either, but I know it was intentional

closed via merge request !13276 (merged)

mentioned in commit 25911e08