Bump actions/checkout from 4 to 6 (#969)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/dev.yml

@@ -15,7 +15,7 @@ jobs:
     name: Render-Book
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: r-lib/actions/setup-r@v2
 

.github/workflows/pr.yml

@@ -18,7 +18,7 @@ jobs:
         run: |
           fork=$(jq --raw-output .pull_request.head.repo.fork "${GITHUB_EVENT_PATH}");echo "fork=${fork}" >> $GITHUB_ENV
 
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: r-lib/actions/setup-r@v2
 

.github/workflows/release.yml

@@ -10,7 +10,7 @@ jobs:
     name: Render-Book
     runs-on: macOS-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: r-lib/actions/setup-r@v2
 

.github/workflows/scheduled-manual-main.yml

@@ -13,7 +13,7 @@ jobs:
     name: Render-Book
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0