chore(deps-dev): bump @wdio/mocha-framework from 6.0.13 to 6.0.15

Bumps [@wdio/mocha-framework](https://github.com/webdriverio/webdriverio) from 6.0.13 to 6.0.15.
- [Release notes](https://github.com/webdriverio/webdriverio/releases)
- [Changelog](https://github.com/webdriverio/webdriverio/blob/master/CHANGELOG.md)
- [Commits](webdriverio/webdriverio@v6.0.13...v6.0.15)

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