Update phpunit gh action config for php8.3

.github/workflows/phpunit.yaml

@@ -17,15 +17,13 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-
-      - name: Install dependencies
-        run: composer install --prefer-dist --no-progress --no-suggest
+      - uses: php-actions/composer@v6
 
       - name: PHPUnit
         uses: php-actions/phpunit@v4
         env:
           DATABASE_URL: mysql://root:[email protected]:${{ job.services.mariadb.ports['3306'] }}/goteo
         with:
-          php_version: '8.3'
+          php_version: 8.3
           php_extensions: pdo_mysql
           configuration:  phpunit.xml.dist