chore(deps): 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](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>

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
     steps:
     - name: Checkout code
       continue-on-error: true
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         submodules: recursive
         fetch-depth: 0
@@ -82,7 +82,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         submodules: recursive
       # ADR-262 P1: `wifi-densepose-rufield` path-deps the `vendor/rufield`
@@ -209,7 +209,7 @@ jobs:
     steps:
     - name: Checkout code
       continue-on-error: true
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         submodules: recursive
 
@@ -276,7 +276,7 @@ jobs:
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     steps:
     - name: Checkout code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         submodules: recursive
 
@@ -346,7 +346,7 @@ jobs:
     steps:
     - name: Checkout code
       continue-on-error: true
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         submodules: recursive
 
@@ -420,7 +420,7 @@ jobs:
       contents: write   # gh-pages deploy needs write (GITHUB_TOKEN is read-only by default -> 403)
     steps:
     - name: Checkout code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         submodules: recursive