Upgrade: karma@^4.0.1, drops Node 6 support, fixes vulnerability #11570
What is the purpose of this pull request? (put an "X" next to item)
[ ] Documentation update
What changes did you make? (Give an overview)
Is there anything you'd like reviewers to focus on?
This version of Karma drops support for Node 6, so it would be a breaking change. I am not labeling this "Breaking" because I assume this can be merged after #11557 is merged. (Labeling "do not merge" here instead.)