avoid using container based php-actions

.github/workflows/ci.yml

@@ -14,16 +14,21 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-
-    - name: Install Composer dependencies
-      uses: php-actions/composer@v5
+
+    - name: Validate composer.json and composer.lock
+      run: composer validate --strict
+
+    - name: Cache Composer packages
+      id: composer-cache
+      uses: actions/cache@v2
       with:
-        php_version: 7.4
-        php_extensions: gettext intl xsl
+        path: vendor
+        key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+        restore-keys: |
+          ${{ runner.os }}-php-
+
+    - name: Install dependencies
+      run: composer install --prefer-dist --no-progress
 
     - name: Run PHPUnit tests
-      uses: php-actions/phpunit@v2
-      with:
-        version: 8.5
-        php_version: 7.4
-        php_extensions: gettext intl xsl
+      run: composer run-script test