update ramsey/composer-install GitHub action to version 2 (#23)

Author: xabbuh

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
           coverage: none
 
       - name: Download dependencies
-        uses: ramsey/composer-install@v1
+        uses: ramsey/composer-install@v2
 
       - name: Run tests
         run: ./bin/console cache:warmup --env dev