Bump actions/checkout from 3 to 4

.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/delete-preview.yaml

@@ -13,7 +13,7 @@ jobs:
         shell: bash -l {0}
     steps:
       - name: Checkout gh-pages branch
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: gh-pages
       - name: Delete preview files

.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/[email protected]
         with:
           access_token: ${{ github.token }}
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Mambaforge
         uses: conda-incubator/setup-miniconda@v2