Bump nikic/php-parser from 4.14.0 to 4.15.1

Bumps [nikic/php-parser](https://github.com/nikic/PHP-Parser) from 4.14.0 to 4.15.1.
- [Release notes](https://github.com/nikic/PHP-Parser/releases)
- [Changelog](https://github.com/nikic/PHP-Parser/blob/master/CHANGELOG.md)
- [Commits](nikic/PHP-Parser@v4.14.0...v4.15.1)

---
updated-dependencies:
- dependency-name: nikic/php-parser
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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