oneOf doesn't work as expected

[doraeric]

Describe the bug
Using oneOf in response content schema doesn't take effect, looks like it only choose the first in oneOf

To Reproduce

1. save the code to example.yml

openapi: "3.0.3"
info:
  title: Test API
  version: "1"
servers:
  - url: https://ipinfo.io
paths:
  /8.8.8.8/json:
    get:
      description: IP
      responses:
        "200":
          description: OK
          content:
            application/json; charset=utf-8:
              schema:
                oneOf:
                  - type: object
                    properties:
                      error:
                        type: string
                  - type: object
                    properties:
                      ip:
                        type: string
                      hostname:
                        type: string
                      anycast:
                        type: boolean
                      city:
                        type: string
                      region:
                        type: string
                      country:
                        type: string
                      loc:
                        type: string
                      org:
                        type: string
                      postal:
                        type: string
                      timezone:
                        type: string
                      readme:
                        type: string
                  

2. run dredd ./example.yml https://ipinfo.io

Expected behavior
pass without error

What is in your dredd.yml?

skip...

What's your dredd --version output?

dredd v14.0.0 (Linux 5.13.19-2-MANJARO; x64)

Note: if you switch the order, it will pass testing