Update workflow

from Universal-Omega/.github (ff4364b27b)

.github/workflows/mediawiki-tests.yml

@@ -346,12 +346,6 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
-          tools: composer:v2
-
-      - name: Composer install
-        if: ${{ matrix.stage == 'phan' }}
-        run: |
-          composer install --prefer-dist --no-progress --no-interaction # $GITHUB_WORKSPACE
 
       - name: Main Test
         continue-on-error: ${{ matrix.experimental }}
@@ -383,7 +377,7 @@ jobs:
               -v "$(pwd)"/src:/mediawiki \
               "${DOCKER_REGISTRY}/${DOCKER_ORG}/${DOCKER_IMAGE}:${DOCKER_LATEST_TAG}" \
               --color
-          elif [ "${{ matrix.stage }}" == 'coverage' ]; then
+          elif [ "${{ matrix.stage }}" == 'coverage' ] && [ -d tests/phpunit ]; then
             docker run \
               -e ZUUL_PROJECT=mediawiki/extensions/"${{ github.event.repository.name }}" \
               -v "$(pwd)"/cache:/cache \