serving/samples/helloworld-nodejs: specifically require package.json (#956)

serving/samples/helloworld-nodejs/Dockerfile

@@ -8,7 +8,7 @@ WORKDIR /usr/src/app
 # Copy application dependency manifests to the container image.
 # A wildcard is used to ensure both package.json AND package-lock.json are copied.
 # Copying this separately prevents re-running npm install on every code change.
-COPY package*.json ./
+COPY package.json package*.json ./
 
 # Install production dependencies.
 RUN npm install --only=production