build(deps-dev): bump php-coveralls/php-coveralls from 2.6.0 to 2.7.0

Bumps [php-coveralls/php-coveralls](https://github.com/php-coveralls/php-coveralls) from 2.6.0 to 2.7.0.
- [Release notes](https://github.com/php-coveralls/php-coveralls/releases)
- [Changelog](https://github.com/php-coveralls/php-coveralls/blob/master/CHANGELOG.md)
- [Commits](php-coveralls/php-coveralls@v2.6.0...v2.7.0)

---
updated-dependencies:
- dependency-name: php-coveralls/php-coveralls
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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