Update actions/checkout version

Author: amaccis

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
       image: amaccis/php-libstemmer:8.1-2.2.0
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Install dependencies
         run: composer install
       - name: Run tests