composer(deps-dev): update mimmi20/coding-standard requirement (#218)

Updates the requirements on [mimmi20/coding-standard](https://github.com/mimmi20/coding-standard) to permit the latest version.
- [Release notes](https://github.com/mimmi20/coding-standard/releases)
- [Commits](mimmi20/coding-standard@2.6.0...2.6.1)

---
updated-dependencies:
- dependency-name: mimmi20/coding-standard
  dependency-type: direct:development
...

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

composer.json

@@ -24,7 +24,7 @@
     "ext-mbstring": "*"
   },
   "require-dev": {
-    "mimmi20/coding-standard": "^2.6.0",
+    "mimmi20/coding-standard": "^2.6.1",
     "phpstan/extension-installer": "^1.1.0",
     "phpstan/phpstan": "^1.4.0",
     "phpstan/phpstan-deprecation-rules": "^1.0.0",