[BUG][typescript-axios] Using allOf with a $ref and an object, along with `withSeparateModelsAndApi` generates broken imports

Created by: olivierbeaulieu

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?
[Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Using allOf with a $ref and an object, along with withSeparateModelsAndApi generates broken imports

openapi-generator version

5.1.0

OpenAPI declaration file content or url

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 -p "withSeparateModelsAndApi=true,modelPackage=models,apiPackage=api"

Steps to reproduce

Run the above command with the provided yaml file
Look at the generated default-api.ts

On line 24, it creates an invalid import statement: import { SomeSchema & object } from '../models';