build: revert config change for actions/checkout@v4

Author: Philip Reichmuth

.github/workflows/ci.yml

@@ -81,7 +81,6 @@ jobs:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
-          ref: ${{ github.head_ref || github.ref_name }}
 
       # Do a dry run of PSR
       - name: Test release