Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

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

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

.github/workflows/build-book.yaml

@@ -52,7 +52,7 @@ jobs:
       run:
         shell: bash -l {0}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Build the book
         run: |
           # copy baltrad notebooks to book dir

.github/workflows/deploy-preview.yaml

@@ -14,7 +14,7 @@ jobs:
       run:
         shell: bash -l {0}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Fetch Repo Name
         id: repo-name
         run: echo "::set-output name=value::$(echo '${{ github.repository }}' | awk -F '/' '{print $2}')"  # just the repo name, not owner

.github/workflows/link-checker.yaml

@@ -35,7 +35,7 @@ jobs:
         uses: styfle/cancel-workflow-action@0.12.0
         with:
           access_token: ${{ github.token }}
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Mambaforge
         uses: conda-incubator/setup-miniconda@v3