Update phpstan/phpstan requirement from 0.12.54 to 0.12.55

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@0.12.54...0.12.55)

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

Author: dependabot-preview[bot]

composer.json

@@ -8,7 +8,7 @@
 		"php-64bit": "*"
 	},
 	"require-dev": {
-		"phpstan/phpstan": "0.12.54",
+		"phpstan/phpstan": "0.12.55",
 		"phpstan/extension-installer": "^1.0",
 		"phpstan/phpstan-strict-rules": "^0.12.4"
 	},