Update orchestra/testbench requirement from ^7.23|^8.1 to ^8.9.1

Updates the requirements on [orchestra/testbench](https://github.com/orchestral/testbench) to permit the latest version.
- [Release notes](https://github.com/orchestral/testbench/releases)
- [Changelog](https://github.com/orchestral/testbench/blob/develop/CHANGELOG-8.x.md)
- [Commits](https://github.com/orchestral/testbench/commits/v8.9.1)

---
updated-dependencies:
- dependency-name: orchestra/testbench
  dependency-type: direct:development
...

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

composer.json

@@ -25,7 +25,7 @@
     },
     "require-dev": {
         "mockery/mockery": "^1.5",
-        "orchestra/testbench": "^7.23|^8.1",
+        "orchestra/testbench": "^8.9.1",
         "phpunit/phpunit": "^9.5.25"
     },
     "autoload": {