Bump php-coveralls/php-coveralls from 2.1.0 to 2.3.0

Bumps [php-coveralls/php-coveralls](https://github.com/php-coveralls/php-coveralls) from 2.1.0 to 2.3.0.
- [Release notes](https://github.com/php-coveralls/php-coveralls/releases)
- [Changelog](https://github.com/php-coveralls/php-coveralls/blob/2.3/CHANGELOG.md)
- [Commits](php-coveralls/php-coveralls@v2.1.0...v2.3.0)

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