Upgrade to actions/checkout v4

Author: carlosame

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
 
     steps:
       # Check-out the repository under $GITHUB_WORKSPACE
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup JDK ${{ matrix.java }}
         uses: actions/setup-java@v4