Gulp and Webpack not async

Question

Why error sync?
"Did you forget to signal async completion?"
tried (cb) at the beginning and end of function buildScripts, same thing.
At this point I pass a training course on frontend development, do everything according to instructions
I can also give a link to the github with the code.

"use strict";

var { watch, src, dest, parallel, series } = require('gulp');

var webpack = require('webpack-stream')

var browserSync = require('browser-sync');
function devServer(cb) {
  var params = {
    watch: true,
    reloadDebounce: 150,
    notify: false,
    server: { baseDir: './build' },
  };
  
  browserSync.create().init(params);
  cb();
}

const { stream } = require('browser-sync');

function buildScripts() {
  return src('src/scripts/**/*.js')
    .pipe(dest('build/scripts/'));
}


function clearBuild() {
  return del('build/');
}


function watchFiles() {
  watch('src/scripts/**/*.js', buildScripts);
}

exports.default =
  series(
    clearBuild,
    parallel(
      devServer,
      series(
        parallel(buildPages, buildStyles, buildScripts, buildAssets),
        watchFiles
      )
    )
  );
...