add back cache statement to deploy workflow

so that setup-node installs yarn for us.

Author: fredvd

.github/workflows/build_deploy.yml

@@ -35,6 +35,7 @@ jobs:
         uses: actions/setup-node@v3
         with:
           node-version: '16'
+          cache: 'yarn'
 
       # node cache
       - name: Get yarn cache directory path