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:
         fetch-depth: 0
 
@@ -81,7 +81,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     # `wifi-densepose-desktop` is a Tauri v2 app — `glib-sys`, `gtk-sys`,
     # `webkit2gtk-sys`, etc. need the Linux dev libraries via pkg-config or the
@@ -188,7 +188,7 @@ jobs:
     steps:
     - name: Checkout code
       continue-on-error: true
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Set up Python ${{ matrix.python-version }}
       continue-on-error: true
@@ -253,7 +253,7 @@ jobs:
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     steps:
     - name: Checkout code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v6
@@ -313,7 +313,7 @@ jobs:
     steps:
     - name: Checkout code
       continue-on-error: true
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Set up Docker Buildx
       continue-on-error: true
@@ -385,7 +385,7 @@ 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
 
     - name: Set up Python
       uses: actions/setup-python@v6