Flaky visual test: Chart legend

The visual regression snapshot for "chart legend default" and "chart legend with long series names and no spaces" has an animation that displays on load and depending on when the storyshot is created, it can cause a visual job failure, as has happened in main here.

You can see the animation here:
https://gitlab-org.gitlab.io/gitlab-ui/?path=/story/charts-chart-legend--default

We need to add some sort of delay when taking snapshots of this component, or find a way to disable the animations for the purpose of testing.