Bump symfony/phpunit-bridge from 4.3.8 to 4.3.9

Bumps [symfony/phpunit-bridge](https://github.com/symfony/phpunit-bridge) from 4.3.8 to 4.3.9.
- [Release notes](https://github.com/symfony/phpunit-bridge/releases)
- [Changelog](https://github.com/symfony/phpunit-bridge/blob/master/CHANGELOG.md)
- [Commits](symfony/phpunit-bridge@v4.3.8...v4.3.9)

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