Bump actions/checkout from 6 to 7 in the gha-dependencies group

Bumps the gha-dependencies group with 1 update: [actions/checkout](https://github.com/actions/checkout).


Updates `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
  dependency-group: gha-dependencies
...

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

Author: dependabot[bot]

.github/workflows/quarto-publish.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out repository
-        uses: actions/checkout@v6 
+        uses: actions/checkout@v7 
 
       - name: Setup Pages
         uses: actions/configure-pages@v6

.github/workflows/validate-pr.yml

@@ -12,7 +12,7 @@ jobs:
     name: Lint & format check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
 
       - uses: astral-sh/setup-uv@v7
         with:
@@ -28,7 +28,7 @@ jobs:
     name: Validate notebook structure
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
 
       - uses: astral-sh/setup-uv@v7
         with:
@@ -50,7 +50,7 @@ jobs:
     name: Quarto render (no deploy)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
 
       - uses: quarto-dev/quarto-actions/setup@v2