Bump infection down for 8.1

Author: dantleech

composer.json

@@ -17,7 +17,7 @@
         "phpstan/phpstan": "^2.0",
         "phpunit/phpunit": "^10.0",
         "symfony/var-dumper": "^7.1",
-        "infection/infection": "^0.31.9",
+        "infection/infection": "^0.29.0",
         "friendsofphp/php-cs-fixer": "^3.91"
     },
     "extra": {