chore(deps): 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/publish-docs.yml

@@ -21,7 +21,7 @@ jobs:
       group: ${{ github.workflow }}-${{ github.ref }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
       - name: Setup Dependencies

.github/workflows/validate.yml

@@ -13,7 +13,7 @@ jobs:
   checks:
     runs-on: blaze/macos-15
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: true
       - run: sudo xcodes select 16.4
@@ -31,7 +31,7 @@ jobs:
         runner: [ macos-15 ]
         rust: [ 1.82.0, stable ]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: true
       - run: sudo xcodes select 16.4