Bump actions/checkout from 6 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/CI.yml

@@ -24,7 +24,7 @@ jobs:
         arch:
           - x64
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: julia-actions/setup-julia@v3
         with:
           version: ${{ matrix.version }}
@@ -43,7 +43,7 @@ jobs:
       actions: write
       contents: read
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: julia-actions/setup-julia@v3
         with:
           version: '1'

.github/workflows/docpreviewcleanup.yml

@@ -16,7 +16,7 @@ jobs:
       contents: write
     steps:
       - name: Checkout gh-pages branch
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         with:
           ref: gh-pages
       - name: Delete preview and history + push changes

.github/workflows/downgrade.yml

@@ -17,7 +17,7 @@ jobs:
       matrix:
         version: ['1.10']
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: julia-actions/setup-julia@v3
         with:
           version: ${{ matrix.version }}