Update to cache@v4

actions/cache#1510

Author: bpbond

.github/workflows/codecov.yaml

@@ -36,7 +36,7 @@ jobs:
         shell: Rscript {0}
 
       - name: Cache R packages
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         with:
           path: ${{ env.R_LIBS_USER }}
           key: macOS-r-4.0-2-${{ hashFiles('.github/depends.Rds') }}