Bump symfony/cache in /buildpacks/buildpack-php/tests/php
Bump symfony/cache in /buildpacks/buildpack-php/tests/php

Bumps [symfony/cache](https://github.com/symfony/cache) from 4.3.7 to 4.3.9.
- [Release notes](https://github.com/symfony/cache/releases)
- [Changelog](https://github.com/symfony/cache/blob/master/CHANGELOG.md)
- [Commits](https://github.com/symfony/cache/compare/v4.3.7...v4.3.9)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
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