Make dividers of new dropdown style full width

Inactive Accountrequested to merge
winh-new-dropdown-dividers into master

What does this MR do?

Increase the width of dropdown dividers so they match the new hover style.

Screenshots

Before After
Screen_Shot_2017-08-03_at_14.28.37 Screen_Shot_2017-08-03_at_14.27.22

What are the relevant issue numbers?

fixes #35784 (closed)

Merge request reports