Issue description markdown ui polish

Summary

When this issue was addressed(gitlab-foss#34338 (moved)) we improved the polish of content in details dropdown but as a result impaired the task list item functionality which is being fixed in this MR(!17557 (merged)). As a result i think this follow up issue needed to be created to address the ui polish of the details dropdown in an issue description while not effecting the functionality of the task list items etc.

Improvements

Currently not sure, we just need to look into the CSS a bit more and figure out a way to accomplish the style request from gitlab-foss#34338 (moved) while keeping style and functionality of the task list items and other description

functionality on par with design

Risks

N/A

Involved components

Possibly https://gitlab.com/gitlab-org/gitlab/blob/master/app%2Fassets%2Fstylesheets%2Fframework%2Ftypography.scss#L70

Design

Remove the bottom margin from <summary>

Current (summary has margin)	Design