This should fix this warning seen in the console when using `swagger-ui-react`:

```
Warning: Received the string `true` for the boolean attribute `readOnly`. Although this works, it will not work as expected if you pass the string "false". Did you mean readOnly={true}?
    in textarea (created by Curl)
    in div (created by Curl)
    in div (created by Curl)
    in Curl (created by LiveResponse)
    in div (created by LiveResponse)
    in LiveResponse (created by Responses)
```

I did not test this change because it's trivial and there is no behavioural change here, React treats non-empty string attributes as `true`.