Update phpstan/phpstan requirement from 0.12.80 to 0.12.81

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@0.12.80...0.12.81)

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

composer.json

@@ -15,7 +15,7 @@
 		"pocketmine/snooze": "^0.1.0"
 	},
 	"require-dev": {
-		"phpstan/phpstan": "0.12.80",
+		"phpstan/phpstan": "0.12.81",
 		"phpstan/phpstan-strict-rules": "^0.12.2"
 	},
 	"autoload": {