Bump phpbench/phpbench from 1.3.1 to 1.4.0 in /tools/phpbench

Bumps [phpbench/phpbench](https://github.com/phpbench/phpbench) from 1.3.1 to 1.4.0.
- [Release notes](https://github.com/phpbench/phpbench/releases)
- [Changelog](https://github.com/phpbench/phpbench/blob/master/CHANGELOG.md)
- [Commits](phpbench/phpbench@1.3.1...1.4.0)

---
updated-dependencies:
- dependency-name: phpbench/phpbench
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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