Update phpstan/phpstan requirement from 1.6.8 to 1.7.7

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@1.6.8...1.7.7)

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

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

composer.json

@@ -40,7 +40,7 @@
         "friendsofphp/php-cs-fixer": "3.8.0",
         "phpunit/phpunit": "^9.5.10",
         "vimeo/psalm": "4.23.0",
-        "phpstan/phpstan": "1.6.8",
+        "phpstan/phpstan": "1.7.7",
         "maglnet/composer-require-checker": "^2.0 || ^3.0",
         "phpro/grumphp-shim": "^0.22.0 || ^1.1"
     },