docs: Changed how to import graphqlHTTP in graphql-express modules

[solidw]

overview

• graphql-js tutorial has an error in running-an-express-graphql-server try to import modules.

I just followed the document at graphql-js tutorials.

But there is problem when I import graphqlHTTP from 'express-grapqhl'.

(The squared black blank is my user name.)

Because they updated express-grapqhl modules and updated official README.md 27 days ago. express-graphql history (see below image)

So I changed require statement in graphql-js tutorials.
var graphqlHTTP = require('express-graphql')
to
var { graphqlHTTP } = require('express-graphql')

And it works!

[danielrearden]

@solidw Thanks for submitting this PR!