GH Actions: version update for ramsey/composer-install

The action used to install Composer packages and handle the caching has released a new major (and some follow-up patch releases), which means, the action reference needs to be updated to benefit from it.

Refs:
* https://github.com/ramsey/composer-install/releases/tag/2.0.0
* https://github.com/ramsey/composer-install/releases/tag/2.0.1
* https://github.com/ramsey/composer-install/releases/tag/2.0.2

Author: jrfnl

.github/workflows/qa.yml

@@ -42,7 +42,7 @@ jobs:
       # Verify the package can be installed succesfully.
       # @link https://github.com/marketplace/actions/install-composer-dependencies
       - name: Install Composer dependencies
-        uses: ramsey/composer-install@v1
+        uses: ramsey/composer-install@v2
 
       - name: Install xmllint
         run: sudo apt-get install --no-install-recommends -y libxml2-utils