build(deps-dev): update phpstan/phpstan requirement from ^1.7 to ^1.9 (#121)

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

Author: dependabot[bot]

composer.json

@@ -22,7 +22,7 @@
         "ergebnis/composer-normalize": "^2.27",
         "infection/infection": "^0.26",
         "phpstan/extension-installer": "^1.1",
-        "phpstan/phpstan": "^1.7",
+        "phpstan/phpstan": "^1.9",
         "phpstan/phpstan-phpunit": "^1",
         "phpunit/phpunit": "^9.5",
         "spatie/phpunit-snapshot-assertions": "^4.2",