composer(deps-dev): update orchestra/testbench requirement (#102)

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/6.x/CHANGELOG-6.x.md)
- [Commits](orchestral/testbench@v6.20.0...v6.20.1)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

composer.json

@@ -26,7 +26,7 @@
     },
     "require-dev": {
         "nunomaduro/larastan": "^0.7.12",
-        "orchestra/testbench": "^6.20.0",
+        "orchestra/testbench": "^6.20.1",
         "phpunit/phpunit": "^9.5",
         "spatie/ray": "^1.30"
     },