babel-preset-react-app: Upgrade @babel/preset-react to 7.9.4 to restore `pragmaFrag` default

Describe the bug

With the current version of babel-preset-react-app, @babel/preset-react is pinned to 7.9.1, which causes errors like this one from Emotion:

https://github.com/emotion-js/emotion/issues/1820

transform-react-jsx: pragma has been set but pragmaFrag has not been set

This has been fixed in @babel/preset-react@7.9.4:

https://github.com/babel/babel/pull/11324#issuecomment-603101768

Did you try recovering your dependencies?

Yes

Which terms did you search for in User Guide?

pragmaFrag
babel
preset
react

Found https://github.com/facebook/create-react-app/pull/8709, which is inexplicably closed.

Environment

Environment Info:

  current version of create-react-app: 3.4.1
  running from /Users/k/.npm/_npx/28361/lib/node_modules/create-react-app

  System:
    OS: macOS 10.15.4
    CPU: (4) x64 Intel(R) Core(TM) i7-6567U CPU @ 3.30GHz
  Binaries:
    Node: 13.12.0 - /usr/local/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.4 - /usr/local/bin/npm
  Browsers:
    Chrome: 81.0.4044.138
    Firefox: 75.0
    Safari: 13.1
  npmPackages:
    react: ^16.13.1 => 16.13.1
    react-dom: ^16.13.1 => 16.13.1
    react-scripts: 3.4.1 => 3.4.1
  npmGlobalPackages:
    create-react-app: 1.3.3

Steps to reproduce

Install Emotion and use as described on the homepage
See the error with pragmaFrag

Expected behavior

No error with pragmaFrag

Actual behavior

Error with pragmaFrag

Reproducible demo

https://github.com/upleveled/react-components-props-state-may-2020

Remove this line: https://github.com/upleveled/react-components-props-state-may-2020/blob/6a0710a88489481ad84dbda4e382ad6ab0e61a07/src/Counter.js#L2