build(deps): bump actions/checkout from 4 to 6 (#6047)

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](https://github.com/actions/checkout/compare/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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/get_real_pr_shas.yml

@@ -22,7 +22,7 @@
 #     needs: real_pr_shas
 #     steps:
 #       - name: Checkout repository
-#         uses: actions/checkout@v4
+#         uses: actions/checkout@v6
 #         with:
 #           fetch-depth: 0  # Full history needed for commit scanning
 # ```
@@ -56,7 +56,7 @@ jobs:
       output_head: ${{ steps.get_shas.outputs.HEAD_SHA }}
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - id: get_shas
         run: |
           git fetch --no-tags --prune --no-recurse-submodules --depth=$((${{ github.event.pull_request.commits }} + 1)) origin ${{ github.event.pull_request.head.sha }}