Bump react/child-process from 0.6.2 to 0.6.4

Bumps [react/child-process](https://github.com/reactphp/child-process) from 0.6.2 to 0.6.4.
- [Release notes](https://github.com/reactphp/child-process/releases)
- [Changelog](https://github.com/reactphp/child-process/blob/master/CHANGELOG.md)
- [Commits](reactphp/child-process@v0.6.2...v0.6.4)

---
updated-dependencies:
- dependency-name: react/child-process
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]