Update phpstan/phpstan requirement from 1.3.1 to 1.3.3 (#126)

Updates the requirements on [phpstan/phpstan](https://github.com/phpstan/phpstan) to permit the latest version.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Changelog](https://github.com/phpstan/phpstan/blob/master/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.3.1...1.3.3)

---
updated-dependencies:
- dependency-name: phpstan/phpstan
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

composer.json

@@ -12,7 +12,7 @@
 		"pocketmine/binaryutils": "^0.2.0"
 	},
 	"require-dev": {
-		"phpstan/phpstan": "1.3.1",
+		"phpstan/phpstan": "1.3.3",
 		"phpstan/phpstan-strict-rules": "^1.0"
 	},
 	"autoload": {