Bump laravel/socialite from 5.14.0 to 5.15.0

Bumps [laravel/socialite](https://github.com/laravel/socialite) from 5.14.0 to 5.15.0.
- [Release notes](https://github.com/laravel/socialite/releases)
- [Changelog](https://github.com/laravel/socialite/blob/5.x/CHANGELOG.md)
- [Commits](laravel/socialite@v5.14.0...v5.15.0)

---
updated-dependencies:
- dependency-name: laravel/socialite
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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