Update twig/twig requirement from ^2.14 to ^2.15
Update twig/twig requirement from ^2.14 to ^2.15

Updates the requirements on [twig/twig](https://github.com/twigphp/Twig) to permit the latest version.
- [Release notes](https://github.com/twigphp/Twig/releases)
- [Changelog](https://github.com/twigphp/Twig/blob/v2.15.1/CHANGELOG)
- [Commits](https://github.com/twigphp/Twig/compare/v2.14.0...v2.15.1)

---
updated-dependencies:
- dependency-name: twig/twig
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
neilime/geshi-twig-extension,neilime/geshi-twig-extension