update readme.md for all samples

Signed-off-by: Anca Iordache <anca.iordache@docker.com>

samples/react-express-mysql/frontend/Dockerfile.production

@@ -1,12 +0,0 @@
-FROM node:10 as build
-
-RUN mkdir /project
-WORKDIR /project
-COPY . .
-RUN yarn install
-RUN yarn run package
-
-FROM nginx:1.13-alpine
-
-COPY config/nginx.conf /etc/nginx/conf.d/default.conf
-COPY --from=build /project/dist /usr/share/nginx/html