Filter ignores some $refs

Hello! I wanted to use the openapi-filter to remove some internal headers from our public openapi specifications. Unfortunately, it doesn’t seem to fully work.

An example:

openapi: 3.0.2
info:
  title: Swagger Petstore - OpenAPI 3.0
  description: omit
  termsOfService: 'http://swagger.io/terms/'
  contact:
    email: [e-mail]
  license:
    name: Apache 2.0
    url: 'http://www.apache.org/licenses/LICENSE-2.0.html'
  version: 1.0.5
servers:
  - url: /api/v3
paths:
  /pet:
    post:
      tags:
        - pet
      summary: Add a new pet to the store
      description: Add a new pet to the store
      operationId: addPet
      parameters:
        - $ref: '#/components/parameters/InternalHeader'
        - $ref: '#/components/parameters/OtherInternalHeader'
        - in: header
          name: X-ThirdInternalHeader
          schema:
            type: string
          required: true
          x-internal: true
      requestBody:
        description: Create a new pet in the store
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Pet'
        required: true
      responses:
        '200':
          description: Successful operation
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Pet'
        '405':
          description: Invalid input

components:
  parameters:
    InternalHeader:
      in: header
      name: X-InternalHeader
      schema:
        type: string
      required: true
      x-internal: true
    OtherInternalHeader:
      in: header
      name: X-OtherInternalHeader
      schema:
        type: string
      required: true
      x-internal: true
  schemas:
    Pet:
      required:
        - name
        - photoUrls
      type: object
      properties:
        id:
          type: integer
          format: int64
          example: 10
      xml:
        name: pet

You can see there are three headers (InternalHeader, OtherInternalHeader & ThirdInternalHeader). After running the openapi-filter the result looks like this:

... omitted because irrelevant
paths:
  /pet:
    post:
      tags:
        - pet
      summary: Add a new pet to the store
      description: Add a new pet to the store
      operationId: addPet
      parameters:
        - $ref: "#/components/parameters/OtherInternalHeader"

...
components:
  parameters: {}
... omitted because irrelevant

In the end all the parameter definitions are removed but the reference to ONE of the two headers is still there.

[MikeRalphson]

Will try and publish today.

[eliasdraexler]

@MikeRalphson Thanks for the merge! When will this be released to npm? I would need the changes for a project.