Fix cache action version in ci

Author: DZunke

.github/workflows/tests.yml

@@ -39,7 +39,7 @@ jobs:
 
       - name: Cache Composer packages
         id: composer-cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: vendor
           key: ${{ runner.os }}-${{ matrix.php }}-${{ hashFiles('**/composer.lock') }}