Right-hand side of `instanceof` does not have to be callable

Flow version: 0.94.0

## Expected behavior

```js
// This should emit an error, e.g. "Right-hand side of 'instanceof' is not callable":
({}) instanceof ({});
```

## Actual behavior

No errors are emitted by Flow, but you'll get a runtime error when running that code.

([Try Flow](https://flow.org/try/#0BQbwvglABAlgdgZwC4EM4GMCmB7AZlUSAbiA))

Related: #7552