Update phpstan/phpstan requirement from ^0.12.26 to ^0.12.27

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@0.12.26...0.12.27)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

composer.json

@@ -20,7 +20,7 @@
     "require-dev": {
         "adriansuter/php-autoload-override": "^1.1",
         "phpspec/prophecy": "^1.10",
-        "phpstan/phpstan": "^0.12.26",
+        "phpstan/phpstan": "^0.12.27",
         "phpunit/phpunit": "^8.5",
         "squizlabs/php_codesniffer": "^3.5"
     },