Bump karma-browserstack-launcher from 1.5.1 to 1.6.0

Bumps [karma-browserstack-launcher](https://github.com/karma-runner/karma-browserstack-launcher) from 1.5.1 to 1.6.0.
- [Release notes](https://github.com/karma-runner/karma-browserstack-launcher/releases)
- [Changelog](https://github.com/karma-runner/karma-browserstack-launcher/blob/master/CHANGELOG.md)
- [Commits](karma-runner/karma-browserstack-launcher@v1.5.1...v1.6.0)

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