Describe the bug
When the request body is a json string, then when getting request body, it is wrapped around additional string quotes.

To Reproduce
Steps to reproduce the behavior:

1. Create the request object

RequestBodyEntity request = Unirest.post("/post")
       .basicAuth("foo", "bar")
       .header("Content-Type", "application/json")
       .queryString("foo", "bar")
       .body("{\"body\": \"sample\"}");

Expected behavior
request.getBody().get().uniPart().getValue().toString() should return "{\"body\": \"sample\"}" but returns ""{\"body\": \"sample\"}"" instead.

Screenshots
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Environmental Data:

• Java Version - 11
• Version [e.g. 3.8.06]

Additional context
Add any other context about the problem here.