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/ci.yml

@@ -19,7 +19,7 @@ jobs:
       lint_result: ${{ steps.lint-outcome.outcome }}
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Validate action.yml Metadata
         id: validate-action-yml
@@ -108,7 +108,7 @@ jobs:
       test_result: ${{ steps.negative-tests-outcome.outcome }}
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Test Case 4 - Composite Action - No Return
         uses: ./
@@ -155,7 +155,7 @@ jobs:
 
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Add Test Summary
         uses: ./
         with: