Updated github action

Author: robjhyndman

.github/workflows/targets.yaml

@@ -57,7 +57,7 @@ jobs:
           sudo apt-get install libzmq3-dev
 
       - name: Cache packages
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         with:
           path: ${{ env.RENV_PATHS_ROOT }}
           key: ${{ runner.os }}-renv-${{ hashFiles('**/renv.lock') }}