Job log scroll-up and scroll-down icons are inconsistent

Summary

The two icons that we use to navigate to the top and bottom of job logs used to match, now they are different shapes:

Screen_Recording_2019-12-09_at_10.17.34_AM

Steps to reproduce

Navigate to the job log view and observe the toolbar at the top of the log.

What is the current bug behavior?

The icons don't match: the scroll-down icon is displayed as two solid arrows pointing down at a line, while the scroll-up icon is displayed as an arrow pointing up at a dot.

What is the expected correct behavior?

The two icons should be the same shape (with one pointing up and one pointing down). The scroll-down icon should still be animated while the job is running.

Possible fixes

Option A: change scroll-up to match scroll-down

This is how it used to look, and it allows us to leave the scroll-down animation alone, but the old icon is not part of gitlab-svgs.

Option B: change scroll-down to match scroll-up

Both icons are in gitlab-svgs, but we would have to adapt the animation to work with the new icon. The old icon has 3 paths with selectors that we use to enable the animation, while the new icon is just one path.