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/CI.yml

@@ -29,7 +29,7 @@ jobs:
         arch:
           - x64
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.version }}
@@ -49,7 +49,7 @@ jobs:
     name: Documentation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
       - uses: cjdoris/julia-downgrade-compat-action@v1
         if: ${{ matrix.version == '1.10' }}

.github/workflows/SpellCheck.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Actions Repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Check spelling
         uses: crate-ci/typos@master