Bump scrivo/highlight.php from 9.18.1.4 to 9.18.1.6
Bump scrivo/highlight.php from 9.18.1.4 to 9.18.1.6

Bumps [scrivo/highlight.php](https://github.com/scrivo/highlight.php) from 9.18.1.4 to 9.18.1.6.
- [Release notes](https://github.com/scrivo/highlight.php/releases)
- [Commits](https://github.com/scrivo/highlight.php/compare/v9.18.1.4...v9.18.1.6)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
phpDocumentor/phpDocumentor2,phpDocumentor/phpDocumentor2,phpDocumentor/phpDocumentor2,phpDocumentor/phpDocumentor2