message: refactor: remove unnecessary httpClient property of KintoneAPIClient
diff: import { RecordClient } from "./client/RecordClient";
  -import { HttpClient, DefaultHttpClient } from "./http/";
  +import { DefaultHttpClient } from "./http/";
  export type Auth = {
  apiToken: string;
  };
  export class KintoneAPIClient {
  - private httpClient: HttpClient;
  record: RecordClient;
  constructor({ subdomain, auth }: { subdomain: string; auth: Auth }) {
  const headers = { "X-Cybozu-API-Token": auth.apiToken };
  const url = `https://${subdomain}.cybozu.com/`;
  - this.httpClient = new DefaultHttpClient({ url, headers });
  + const httpClient = new DefaultHttpClient({ url, headers });
  - this.record = new RecordClient(this.httpClient);
  + this.record = new RecordClient(httpClient);
  }
  }
  