Bump karma from 5.2.3 to 6.3.4 in /build

Bumps [karma](https://github.com/karma-runner/karma) from 5.2.3 to 6.3.4.
- [Release notes](https://github.com/karma-runner/karma/releases)
- [Changelog](https://github.com/karma-runner/karma/blob/master/CHANGELOG.md)
- [Commits](https://github.com/karma-runner/karma/compare/v5.2.3...v6.3.4

)

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

Signed-off-by: dependabot[bot] <support@github.com>