update GitHub Action »Checkout« to v6

Author: agebhar1

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
     name: Java ${{ matrix.javaVersion }}-${{ matrix.javaDistribution }}
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - uses: actions/setup-java@v4
         with:
           distribution: ${{ matrix.javaDistribution }}