Migration to Gutenberg: Remove references to react

[ItsJonQ]

Due to how the JS code is compiled, Gutenberg React code does not start with the standard import React from 'react';.

Hooks and utils that come from the react package would instead come from @wordpress/element.

For example, we'll need to refactor code from this:

import React, { useRef }  from 'react'

to:

import { useRef } from '@wordpress/element';

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This is something we'll either do as a final step within this @itsjonq/g2 repo before migration. Or, this is something we'll refactor when the code lands within Gutenberg.

[ItsJonQ]

We'll do this when we copy/paste the files into Gutenberg. Moving this to Phase 2.