docs: fix --client-progress example (#3189)

Author: snitin315

examples/cli/progress/README.md

@@ -1,7 +1,7 @@
 # CLI: Progress Option
 
 ```shell
-npm run webpack-dev-server -- --open
+npm run webpack-dev-server -- --open --client-progress
 ```
 
 ## What Should Happen

examples/cli/progress/webpack.config.js

@@ -7,7 +7,4 @@ const { setup } = require('../../util');
 module.exports = setup({
   context: __dirname,
   entry: './app.js',
-  client: {
-    progress: true,
-  },
 });