Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/ci.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 📥 Check-out
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: 🧰 Install JDK
         uses: actions/setup-java@v4
         with:
@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 📥 Check-out
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: 🧰 Install JDK
         uses: actions/setup-java@v4
         with:
@@ -36,7 +36,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 📥 Check-out
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: 🧰 Install JDK
         uses: actions/setup-java@v4
         with:
@@ -50,7 +50,7 @@ jobs:
     runs-on: macOS-latest
     steps:
       - name: 📥 Check-out
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: 🧰 Install JDK
         uses: actions/setup-java@v4
         with:
@@ -81,7 +81,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 📥 Check-out
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: 🚀 Create GitHub release
         uses: softprops/action-gh-release@v2
         with: