Update workflow to fix an issue with MacOS

Author: giabaio

.github/workflows/check-standard.yaml

@@ -54,6 +54,7 @@ jobs:
       - uses: r-lib/actions/setup-r-dependencies@v2
         with:
           dependencies: '"all"'
+          cache: ${{ matrix.config.os != 'macOS-latest' }}
           extra-packages: |
             rcmdcheck
             rstan