Update league/oauth2-server requirement from ^8.1 to ^9.0

Updates the requirements on [league/oauth2-server](https://github.com/thephpleague/oauth2-server) to permit the latest version.
- [Release notes](https://github.com/thephpleague/oauth2-server/releases)
- [Changelog](https://github.com/thephpleague/oauth2-server/blob/master/CHANGELOG.md)
- [Commits](thephpleague/oauth2-server@8.1.0...9.0.0)

---
updated-dependencies:
- dependency-name: league/oauth2-server
  dependency-type: direct:production
...

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

composer.json

@@ -6,7 +6,7 @@
   "require": {
     "php": ">=8.1",
     "codeigniter4/framework": "^4.0",
-    "league/oauth2-server": "^8.1",
+    "league/oauth2-server": "^9.0",
     "laminas/laminas-diactoros": "^3.3.1",
     "steverhoades/oauth2-openid-connect-server": "^2.0"
   },