Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -9,7 +9,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Copy CI gradle.properties
         run: mkdir -p ~/.gradle ; cp .github/ci-gradle.properties ~/.gradle/gradle.properties

.github/workflows/documentation.yml

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up JDK 22
         uses: actions/setup-java@v5

.github/workflows/publish.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: macOS-latest
     steps:
       - name: Check out code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set up JDK 22
         uses: actions/setup-java@v5
         with:

.github/workflows/schema-validation.yml

@@ -15,7 +15,7 @@ jobs:
 
     steps:
     - name: Checkout code
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
 
     - name: Set up JDK 22
       uses: actions/setup-java@v5