chore(deps): update actions/checkout action to v6

Author: renovate-bot

.github/workflows/gradle-dependency-submit.yaml

@@ -18,7 +18,7 @@ jobs:
       contents: write
     steps:
     - name: Checkout sources
-      uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
       with:
         persist-credentials: false
     - name: Set up JDK 21

.github/workflows/gradle-wrapper-validation.yml

@@ -6,5 +6,5 @@ jobs:
     name: "Validation"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: gradle/actions/wrapper-validation@v5

.github/workflows/main.yml

@@ -27,7 +27,7 @@ jobs:
       # Number of jobs to generate in matrix.js
       MATRIX_JOBS: 4
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - id: set-matrix
         run: |
           node .github/workflows/matrix.js
@@ -43,7 +43,7 @@ jobs:
       fail-fast: false
       # max-parallel: 4
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 50
     - name: Set up Java ${{ matrix.java_version }}, oracle
@@ -92,7 +92,7 @@ jobs:
     name: 'Error Prone (JDK 21)'
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: 'Set up JDK 21'
       uses: actions/setup-java@v5
       with: