Bump qunit from 2.20.1 to 2.21.0 (#936)

Bumps [qunit](https://github.com/qunitjs/qunit) from 2.20.1 to 2.21.0.
- [Release notes](https://github.com/qunitjs/qunit/releases)
- [Changelog](https://github.com/qunitjs/qunit/blob/main/History.md)
- [Commits](qunitjs/qunit@2.20.1...2.21.0)

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

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Author: dependabot[bot]