Bump phpstan version

Author: szepeviktor

composer.json

@@ -13,7 +13,7 @@
     "require": {
         "php": "~7.1",
         "php-stubs/wordpress-stubs": "^4.7 || ^5.0",
-        "phpstan/phpstan": "^0.12.0",
+        "phpstan/phpstan": "^0.12.26",
         "symfony/polyfill-php73": "^1.12.0"
     },
     "require-dev": {