update mongoose version on node code example

Example 1: how to install mongoose

$ npm install mongoose

Example 2: mongoose npm

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/my_database', {
    useNewUrlParser: true,
    useUnifiedTopology: true,
    useFindAndModify: false,
    useCreateIndex: true
  })
  .then(()=> console.log('connect'))
  .catch((error) => console.error(error));