[PHP]: Update phpstan/phpstan requirement from 1.10.14 to 1.10.15

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/1.11.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.10.14...1.10.15)

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

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

composer.json

@@ -18,7 +18,7 @@
     "require-dev": {
         "ext-ast": "*",
         "bamarni/composer-bin-plugin": "^1.4",
-        "phpstan/phpstan": "1.10.14",
+        "phpstan/phpstan": "1.10.15",
         "phpstan/phpstan-phpunit": "1.3.11",
         "rector/rector": "0.16.0",
         "roave/security-advisories": "dev-master",