build(deps-dev): bump phpstan/phpstan from 0.12.17 to 0.12.18 (#12)

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 0.12.17 to 0.12.18.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Commits](phpstan/phpstan@0.12.17...0.12.18)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]