chore(deps-dev): update rector/rector requirement from 0.18.7 to 0.18.8

Updates the requirements on [rector/rector](https://github.com/rectorphp/rector) to permit the latest version.
- [Release notes](https://github.com/rectorphp/rector/releases)
- [Commits](rectorphp/rector@0.18.7...0.18.8)

---
updated-dependencies:
- dependency-name: rector/rector
  dependency-type: direct:development
...

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

composer.json

@@ -33,7 +33,7 @@
  "phpunit/phpcov": "^8.2",
  "phpunit/phpunit": "^9.1",
  "predis/predis": "^1.1 || ^2.0",
- "rector/rector": "0.18.7",
+ "rector/rector": "0.18.8",
  "vimeo/psalm": "^5.0"
  },
  "suggest": {