Improve dropdown position in Modal windown

Problem

When I review an MR, I find out if there is a dropdown which at the edge of the modal content like the gif shows below;

Problems it causes:

• It is not very easy to realise that there is more content in the dropdown
• With the double scrolling, it becomes challenging to use.

Proposal

I have two proposals below; what do you all think?

Float up	Float outside of the modal window

cc: @gitlab-com/gitlab-ux/designers