[0.55] regression - react synthetic events (try flow bug only?)

`SyntheticEvent`s appear to not be included in [55](https://flow.org/try/#0JYWwDg9gTgLgBAKjgQwM5wEoFNkGN4BmUEIcA5FDvmQNwBQdMAnmFnAArFjoC8cA3nThwIAOwDCAC2SiA5lgD8ALjgAKAG7IANgFcsKhahhRgcgJRweAPjjqIwACZ0AvvTq4tadAFkm4kpCiWKLwWAAeMMEO6Nh4MAB0-uBiwTAAPJwQ3DaCwtKiDlpY4lrAuADWlmr6cADKTCGSWDBlAKLqqWlWFtYCdACQuGJGAmJSMvLOVTCSwKjxYFyoQsJwwARqY-nyFrmrwlsTWKpkBBAQcB5l5VgOZGYrws4rz8IrlAVYUKq7j3CUMB0UFEcDSDmA6hEElKFR4-Bmc3i+UKxRh5WcVjOEDSAHpweorPQni4GGlfElAqk4DjCUA), but works in [54.1 and lower](https://flow.org/try/#0JYWwDg9gTgLgBAKjgQwM5wEoFNkGN4BmUEIcA5FDvmQNwBQdMAnmFnAArFjoC8cA3nThwIAOwDCAC2SiA5lgD8ALjgAKAG7IANgFcsKhahhRgcgJRweAPjjqIwACZ0AvvTq4tadAFkm4kpCiWKLwWAAeMMEO6Nh4MAB0-uBiwTAAPJwQ3DaCwtKiDlpY4lrAuADWlmr6cADKTCGSWDBlAKLqqWlWFtYCdACQuGJGAmJSMvLOVTCSwKjxYFyoQsJwwARqY-nyFrmrwlsTWKpkBBAQcB5l5VgOZGYrws4rz8IrlAVYUKq7j3CUMB0UFEcDSDmA6hEElKFR4-Bmc3i+UKxRh5WcVjOEDSAHpweorPQni4GGlfElAqk4DjCUA)

Test code (linked above):

```javascript
import * as React from 'react';

type Props = {
onChange?: (value: ?string) => void
};

class MyComponent extends React.Component {
handleClick = (e: SyntheticEvent<>) => {
const {onChange} = this.props
if (onChange) {
onChange('foo clicked')
}
}

render() {
return

;
```

```
8: handleClick = (e: SyntheticEvent<>) => {
^ identifier `SyntheticEvent`. Could not resolve name
```

This seems like a regression, because these SyntheticEvents are still in the libdef https://github.com/facebook/flow/blob/v0.55.0/lib/react-dom.js

and recommended to be used by https://flow.org/en/docs/react/events/

Here is an exact [55 try flow of the docs example](https://flow.org/try/#0JYWwDg9gTgLgBAKjgQwM5wEoFNkGN4BmUEIcA5FDvmQNwBQduANmugLICeAwiZAHZY+8LAA8YggCbpseGADoe4CAKEAeAN4BfADRx1cXBACuQgFxw+RkACMsUOJoB8eunDgALZHwlMsXJsC4ANZwALxwABRYAG6CMOYAyhxC7lgwgQCisWoAEgAqbAAyAEJGMDDKGb4gcY4AlGHO6q5ucAD0bXB5ECi4uFio6BzG9tZlFXxwwHyoMF79cEaoWHAABjFxcrhGUJRCechQAOZpq3ItblHZ8tu7cQfHaeb5RaXlldVxdfQXcDDuwFQcmWMASc3EETAlGiYOQ4kakWarVahhM8TgUJisPEW2MQm0v00dW+LU0PzcewkdgiDSRrUoMB2kwivzcqgkwGijlZrVUYEcPDR5nU-0BwPBWFxaM0qja-J5bLG70myn8gSCoRFAKBnm8vjVwScCtaAEk+LhKDUhMbZUqJtzkWy2hyub8SW5NHRNEA), which also works in 54.1 and lower.

I actually came to report a different issue and when trying to boil down the test case, perhaps this is the root cause.