Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/maven.yml

@@ -18,7 +18,7 @@ jobs:
     name: on ${{ matrix.os }}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up JDK ${{ matrix.java }}
         uses: actions/setup-java@v3