updated phpstan to 12 for the generator

Author: Kharhamel

generator/composer.json

@@ -17,8 +17,8 @@
   },
   "require-dev": {
     "phpunit/phpunit": "^7",
-    "phpstan/phpstan": "^0.11.16",
-    "thecodingmachine/phpstan-strict-rules": "^0.10.3",
+    "phpstan/phpstan": "^0.12",
+    "thecodingmachine/phpstan-strict-rules": "^0.12",
     "squizlabs/php_codesniffer": "^3.2",
     "php-coveralls/php-coveralls": "^2.1"
   },