Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/build.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5.0.0
+      - uses: actions/checkout@v6.0.0
       - uses: gradle/wrapper-validation-action@v3
       - name: Set up JDK
         uses: actions/setup-java@v4

.github/workflows/upload.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5.0.0
+      - uses: actions/checkout@v6.0.0
       - uses: gradle/wrapper-validation-action@v3
       - name: Set up JDK
         uses: actions/setup-java@v4