Remove cjs file (#6590)

packages/next/build/webpack-config.ts

@@ -12,7 +12,7 @@ import { ReactLoadablePlugin } from './webpack/plugins/react-loadable-plugin'
 import { SERVER_DIRECTORY, REACT_LOADABLE_MANIFEST, CLIENT_STATIC_FILES_RUNTIME_WEBPACK, CLIENT_STATIC_FILES_RUNTIME_MAIN } from 'next-server/constants'
 import { NEXT_PROJECT_ROOT, NEXT_PROJECT_ROOT_NODE_MODULES, NEXT_PROJECT_ROOT_DIST_CLIENT, PAGES_DIR_ALIAS, DOT_NEXT_ALIAS } from '../lib/constants'
 import AutoDllPlugin from 'autodll-webpack-plugin'
-import TerserPlugin from './webpack/plugins/terser-webpack-plugin/src/cjs.js'
+import {TerserPlugin} from './webpack/plugins/terser-webpack-plugin/src/index'
 import { ServerlessPlugin } from './webpack/plugins/serverless-plugin'
 import { WebpackEntrypoints } from './entries'
 type ExcludesFalse = <T>(x: T | false) => x is T

packages/next/build/webpack/plugins/terser-webpack-plugin/src/cjs.js

-const plugin = require('./index');
-
-module.exports = plugin.default;

packages/next/build/webpack/plugins/terser-webpack-plugin/src/index.js

@@ -12,7 +12,7 @@ const warningRegex = /\[.+:([0-9]+),([0-9]+)\]/;
 
 const JS_REGEX = /\.m?js$/
 
-class TerserPlugin {
+export class TerserPlugin {
   constructor(options = {}) {
     const {
       terserOptions = {},
@@ -306,5 +306,3 @@ class TerserPlugin {
     });
   }
 }
-
-export default TerserPlugin;