fs: remove redundant code in readableWebStream()

[deokjinkim]

Remove redundant code by moving it to outside of if/else. Plus, make options optional in doc.

Below code is duplicated because it exists on both if and else.

    const {
      readableStreamCancel,
    } = require('internal/webstreams/readablestream');
    this[kRef]();
    this.once('close', () => {
      readableStreamCancel(readable);
    });

And options param is optional like below.

  /**
   * @typedef {import('../webstreams/readablestream').ReadableStream
   * } ReadableStream
   * @param {{
   *   type?: string;
   *   }} [options]
   * @returns {ReadableStream}
   */
  readableWebStream(options = kEmptyObject) {

[debadree25]

Thanks 😄

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/53541/

[nodejs-github-bot]

Landed in c5cad08