ci: do not force phpunit version

Signed-off-by: grnd-alt <[email protected]>

Author: grnd-alt

.github/workflows/integration.yml

@@ -63,7 +63,6 @@ jobs:
           auth_header="$(git config --local --get http.https://github.com/.extraheader)"
           git submodule sync --recursive
           git -c "http.extraheader=$auth_header" -c protocol.version=2 submodule update --init --force --recursive --depth=1
-          cd build/integration && composer require --dev phpunit/phpunit:~9
 
       - name: Checkout app
         uses: actions/[email protected]