Bump actions/checkout from 5 to 6 (#263)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/DocPreviewCleanup.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout gh-pages branch
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           ref: gh-pages
 

.github/workflows/Documenter.yml

@@ -29,7 +29,7 @@ jobs:
     outputs:
       doxygen_dir: ${{ steps.determine_doxygen_dir.outputs.doxygen_dir }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         with:
           version: '1.10'
@@ -62,7 +62,7 @@ jobs:
     needs: build-docs
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install doxygen
         run: |
           sudo apt-get install -y doxygen

.github/workflows/SpellCheck.yml

@@ -8,6 +8,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Actions Repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Check spelling
         uses: crate-ci/typos@v1.39.0

.github/workflows/ci.yml

@@ -52,7 +52,7 @@ jobs:
       JULIA_DEPOT_PATH: ~/.julia
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Enable Julia cache
         uses: julia-actions/cache@v2