build(deps-dev): bump phpstan/phpstan from 0.12.48 to 0.12.50 (#50)

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 0.12.48 to 0.12.50.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Commits](phpstan/phpstan@0.12.48...0.12.50)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]