Simplify checkout step in code-style workflow

Removed unnecessary 'with' block for checkout step.

Author: tabuna

.github/workflows/code-style.yml

@@ -17,8 +17,6 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v6
-        with:
-          ref: ${{ github.head_ref }}
 
       - name: Setup PHP 🔧
         uses: shivammathur/setup-php@v2