Download menu expands past the fold and doesn't auto size to the bottom height of the browser window

Summary

Download menu expands past the fold and doesn't auto size to the bottom height of the browser window

Steps to reproduce

1. Visit https://gitlab.com/gitlab-org/gitlab-ce/tree/master
2. Click Download button

What is the current bug behavior?

Download menu expands past the fold and doesn't auto size to the visible bottom height of the browser window

What is the expected correct behavior?

I'm assuming it should auto size to the visible bottom of the browser window + padding/margin @tauriedavis ?

Output of checks

This bug happens on GitLab.com

Possible fixes