Authorization from Dev portal doesn't work for Oauth2 clientCredentials flow integration with Okta

Hello!

Authorization button doesn't work with Okta JWT token provider and `clientCredentials` flow.

Having `securitySchemes` section like:

securitySchemes:
  publicApiKey:
    type: apiKey
    name: Authorization
    in: header
  myOAuth2:
    type: oauth2
    flows:
      clientCredentials:
        tokenUrl: https://my.okta.com/oauth2/default/v1/token
        scopes:
	  api_public: access to the endpoint

Dev portal web UI always sends `origin` header. Okta responds with `Access-Control-Allow-Origin` when creds are valid, but the response code is 401 and the body:

{
    "error": "invalid_client",
    "error_description": "Browser requests to the token endpoint must use Proof Key for Code Exchange."
}

because of https://support.okta.com/help/s/article/Browser-requests-to-the-token-endpoint-must-use-Proof-Key-for-Code-Exchange.

Thus, I question is it possible to change something on Apigee side to prevent sending `origin` header at least for the `clientCredentials` flow?

My point here: any server besides Okta should consider requests with `origin` header as browser requests and thus it has its right to respond with an error when it expects a call from a server.

----
This is not similar but close to https://community.apigee.com/questions/61809/dev-portal-invocation-external-oauth.html as Okta is customizable and can respond with the same header as the origin in the CORS header.