Decrease vertical margin in empty tasklist

What does this MR do and why?

There's a lot of extra vertical margin in empty task lists (and it looked slightly uneven)

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Look at an empty task list on an issue

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.