axios bug repro case v0.21.1 vs. v0.21.2

package.json

{
  "name": "axios-repro",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "DEBUG=nock.scope* mocha test.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@slack/web-api": "^6.4.0",
    "axios": "0.21.1",
    "mocha": "^9.1.1",
    "nock": "^13.1.3"
  }
}

test.js

const nock = require('nock');
const { WebClient } = require('@slack/web-api');
const token = 'xoxb-faketoken';
const assert = require('assert');

describe('has all admin.usergroups.* APIs', function () {
  function verify(runApiCall, methodName, expectedBody, done) {
    const scope = nock('https://slack.com')
      .post(`/api/${methodName}`)
      .reply(200, function (_uri, body) {
        return { ok: true, body: body };
      });

    runApiCall
      .then((res) => {
        assert(res.body === expectedBody);
        scope.done();
        done();
      });
  }
  const client = new WebClient(token, { logLevel: 'debug' });

  it('can call admin.usergroups.addChannels with a string "channel_ids"', function (done) {
    verify(
      client.admin.usergroups.addChannels({ team_id: 'T123', usergroup_id: 'S123', channel_ids: 'C123,C234' }),
      'admin.usergroups.addChannels',
      'token=xoxb-faketoken&team_id=T123&usergroup_id=S123&channel_ids=C123%2CC234',
      done,
    );
  });
});