Bump humbug/php-scoper from 0.18.3 to 0.18.4

Bumps [humbug/php-scoper](https://github.com/humbug/php-scoper) from 0.18.3 to 0.18.4.
- [Release notes](https://github.com/humbug/php-scoper/releases)
- [Commits](humbug/php-scoper@0.18.3...0.18.4)

---
updated-dependencies:
- dependency-name: humbug/php-scoper
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>