build: only check --engine-strict for production deps (#810)

Co-authored-by: Justin Beckwith <justin.beckwith@gmail.com>

synthtool/gcp/templates/node_library/.github/workflows/ci.yaml

@@ -16,7 +16,11 @@ jobs:
         with:
           node-version: ${{ '{{' }} matrix.node {{ '}}' }}
       - run: node --version
-      - run: npm install --engine-strict
+      # The first installation step ensures that all of our production
+      # dependencies work on the given Node.js version, this helps us find
+      # dependencies that don't match our engines field:
+      - run: npm install --production --engine-strict
+      - run: npm install
       - run: npm test
       - name: coverage
         uses: codecov/codecov-action@v1