Bump actions/checkout from 5 to 6 (#164)

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

Author: dependabot[bot]

.github/workflows/Documenter.yml

@@ -37,7 +37,7 @@ jobs:
       group: ${{ github.workflow }}-${{ github.ref }}
       cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         with:
           version: '1'

.github/workflows/PreviewCleanup.yml

@@ -16,7 +16,7 @@ jobs:
       contents: write
     steps:
       - name: Checkout gh-pages branch
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           ref: gh-pages
       - name: Delete preview and history + push changes

.github/workflows/UnitTests.yml

@@ -44,7 +44,7 @@ jobs:
           - true
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: julia-actions/setup-julia@v2
       with:
         version: ${{ matrix.julia_version }}
@@ -69,7 +69,7 @@ jobs:
           - ubuntu-latest
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: julia-actions/setup-julia@v2
       with:
         version: ${{ matrix.julia_version }}