dependency: Update actions/checkout action to v6 (#113)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/gradle.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up JDK 21
         uses: actions/setup-java@v5

.github/workflows/publish-release.yml

@@ -11,7 +11,7 @@ jobs:
     environment: deployment
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up JDK 21
         uses: actions/setup-java@v5