Remove phpunit requirement as it is already required by the TF

Author: linawolf

Documentation/Testing/UnitTesting/Running.rst

@@ -17,8 +17,7 @@ PHPUnit and the testing framework via Composer as a development dependency:
 ..  code-block:: bash
 
     composer require --dev \
-      "typo3/testing-framework":"^9.3.0" \
-      "phpunit/phpunit":"^11.2.5"
+      "typo3/testing-framework":"^9.3.0"
 
 Which versions to use depends on the PHP and TYPO3 versions to be supported.