Bump actions/checkout from 5 to 6 (#48)

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/CI.yml

@@ -35,7 +35,7 @@ jobs:
         arch:
           - x64
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.version }}
@@ -74,7 +74,7 @@ jobs:
     name: Codestyle
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         with:
           version: '1'

.github/workflows/Downstream.yml

@@ -22,7 +22,7 @@ jobs:
         include:
           - package: 'DocumenterCitations'
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         with:
           version: 'lts'

.github/workflows/documentation.yml

@@ -21,7 +21,7 @@ jobs:
       pull-requests: read
       statuses: write
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: julia-actions/setup-julia@v2
         with:
           version: '1'