Update GH actions

Author: fingolfin

.github/workflows/CI.yml

@@ -41,13 +41,13 @@ jobs:
             os: macOS-latest
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           # For Codecov, we must also fetch the parent of the HEAD commit to
           # be able to properly deal with PRs / merges
           fetch-depth: 2
       - name: "Set up Julia"
-        uses: julia-actions/setup-julia@v1
+        uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.julia-version }}
           arch: ${{ matrix.julia-arch }}
@@ -76,7 +76,7 @@ jobs:
     name: Documentation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: julia-actions/cache@v1
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-docdeploy@latest

.github/workflows/CleanupDocPreview.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout gh-pages branch
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           ref: gh-pages
       - name: Delete preview