[BUG][typescript-axios] Using the allOf description with a combination of $ref and an object results in a wrong typing

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

Using the typescript-axios generator fails to properly generate the client when using allOf with a combination of a $ref and an object.

openapi-generator version

5.1.0

OpenAPI declaration file content or url

swagger.yml:

openapi: 3.0.2
info:
  title: hello
  version: 1.0.0
components:
  schemas:
    SomeSchema:
      type: object
      properties:
        some_prop:
          type: integer
paths:
  /foobar:
    get:
      responses:
        '200':
          description: ok
          content:
            application/json:
              schema:
                allOf:
                  - $ref: '#/components/schemas/SomeSchema'
                  - type: object
                    properties:
                      foobar: 
                        type: string

Generation Details

openapi-generator-cli generate -i http://localhost:8000/swagger.yml -g typescript-axios -o foo

Steps to reproduce

1. Run the above script
2. Look at the generated api.ts
3. Notice that foobarGet returns AxiosPromise<SomeSchema & object>

I would expect the return type to be AxiosPromise<SomeSchema & { foobar?: string }>

Run the stated openapi-generator-cli command against the provided swagger.yml and inspect the generated api.ts, focusing on the typescript-axios handling of the allOf response. Done means the generated foobarGet return type includes SomeSchema & { foobar?: string } rather than SomeSchema & object, while preserving the reproduction behavior.