Remove React import

[MartijnHols]

After #4086, #4087, #4088 we can remove the React import from our files.

• Follow instructions in https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html#removing-unused-react-imports to remove the React import from all files
• Update eslint-config overrides with these new rules: https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html#eslint

Blocked by facebook/create-react-app#9877