Update versions of public GH Actions.

.github/workflows/pkgdown.yaml

@@ -11,11 +11,11 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - uses: r-lib/actions/setup-r@v2
         with:
-          r-version: '4.2' # The R version to download (if necessary) and use.
+          r-version: '4.4' # The R version to download (if necessary) and use.
 
       - uses: r-lib/actions/setup-pandoc@v2
 
@@ -27,7 +27,7 @@ jobs:
         shell: Rscript {0}
 
       - name: Restore R package cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ${{ env.R_LIBS_USER }}
           key: ${{ runner.os }}-${{ hashFiles('.github/R-version') }}-1-${{ hashFiles('.github/depends.Rds') }}