Bump phpstan/phpstan from 2.2.5 to 2.2.8 in /plugins/basicrum

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan-phar-composer-source) from 2.2.5 to 2.2.8.
- [Commits](https://github.com/phpstan/phpstan-phar-composer-source/commits)

---
updated-dependencies:
- dependency-name: phpstan/phpstan
  dependency-version: 2.2.8
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]