Update phpstan/phpstan requirement from 0.12.20 to 0.12.22

Updates the requirements on [phpstan/phpstan](https://github.com/phpstan/phpstan) to permit the latest version.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Commits](phpstan/phpstan@0.12.20...0.12.22)

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

Author: dependabot-preview[bot]

composer.json

@@ -19,7 +19,7 @@
     },
     "require-dev": {
         "doctrine/coding-standard": "^7.0",
-        "phpstan/phpstan": "0.12.20",
+        "phpstan/phpstan": "0.12.22",
         "phpstan/phpstan-phpunit": "0.12.8",
         "phpstan/phpstan-strict-rules": "0.12.2",
         "phpunit/phpunit": "^8.5",