dillon1000/react

Move modern strict to experimental (#28152)

Turn this on 

Edited: ope, nvm
<details>
Looks like there's still an outstanding issue with this. The original PR
turned off a strict effects test, which causes a stray
`componentWillUnmount` to fire.


https://github.com/facebook/react/commit/5d1ce651393524639a3b4b1e861a0413a4d25629#diff-19df471970763c4790c2cc0811fd2726cc6a891b0e1d5dedbf6d0599240c127aR70


Before:
```js
expect(log).toEqual([
      'constructor',
      'constructor',
      'getDerivedStateFromProps',
      'getDerivedStateFromProps',
      'render',
      'render',
      'componentDidMount',
    ]);
```

After:

```js
expect(log).toEqual([
      'constructor',
      'constructor',
      'getDerivedStateFromProps',
      'getDerivedStateFromProps',
      'render',
      'render',
      'componentDidMount',
      'componentWillUnmount',
      'componentDidMount',
    ]);
```

So there's a bug somewhere
</details>