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] <[email protected]>

Author: dependabot[bot]

.github/workflows/release.yaml

@@ -13,7 +13,7 @@ jobs:
       pull-requests: write
       packages: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: "Publish Features"
         uses: devcontainers/action@v1

.github/workflows/test.yaml

@@ -28,7 +28,7 @@ jobs:
           # - ubuntu:latest
           - mcr.microsoft.com/devcontainers/base:ubuntu
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: "Install latest devcontainer CLI"
         run: npm install -g @devcontainers/cli
@@ -47,7 +47,7 @@ jobs:
           - codespaces-dotfiles
           - powershell-extended
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: "Install latest devcontainer CLI"
         run: npm install -g @devcontainers/cli
@@ -59,7 +59,7 @@ jobs:
   #   runs-on: ubuntu-latest
   #   continue-on-error: true
   #   steps:
-  #     - uses: actions/checkout@v4
+  #     - uses: actions/checkout@v6
 
   #     - name: "Install latest devcontainer CLI"
   #       run: npm install -g @devcontainers/cli

.github/workflows/validate.yml

@@ -13,7 +13,7 @@ jobs:
     env:
       FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: 'true'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: "Validate devcontainer-feature.json files"
         uses: devcontainers/action@v1