Bump karma from 6.3.20 to 6.4.0

Bumps [karma](https://github.com/karma-runner/karma) from 6.3.20 to 6.4.0.
- [Release notes](https://github.com/karma-runner/karma/releases)
- [Changelog](https://github.com/karma-runner/karma/blob/master/CHANGELOG.md)
- [Commits](karma-runner/karma@v6.3.20...v6.4.0)

---
updated-dependencies:
- dependency-name: karma
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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