Update phpstan/phpstan requirement from 1.5.3 to 1.6.3

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/1.7.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.5.3...1.6.3)

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

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

composer.json

@@ -26,7 +26,7 @@
     },
     "require-dev": {
         "nette/tester": "2.4.2",
-        "phpstan/phpstan": "1.5.3",
+        "phpstan/phpstan": "1.6.3",
         "phpstan/phpstan-strict-rules": "1.1.0",
         "nepada/phpstan-nette-tester": "0.4.0",
         "spaze/phpstan-disallowed-calls": "2.3.1",