fix: update .gitlab-ci.yml for php 8.1 support

This commit removes unnecessary inputs and the entire phpunit-php8.1 block from .gitlab-ci.yml,
enabling PHPUnit to run on PHP 8.1 in the pipeline.

.gitlab-ci.yml

 include:
   - component: dev.quiqqer.com/quiqqer/stabilization/ci-cd-components/quiqqer-package-bundle/quiqqer-package-bundle@2
-    inputs:
-      quiqqer-major-version: 1
 
 # Remove the entire phpunit-php8.1 block, to allow PHPUnit to run on PHP 8.1 in your pipeline
 phpunit-php8.1: