fix(babel-migrator): transform babel preset regardless of plugin version (#4633)

Author: haoqunjiang

packages/@vue/cli-plugin-babel/migrator/index.js

@@ -1,15 +1,15 @@
 const { chalk } = require('@vue/cli-shared-utils')
 
 module.exports = (api) => {
+  api.transformScript('babel.config.js', require('../codemods/usePluginPreset'))
+
   if (api.fromVersion('^3')) {
     api.extendPackage({
       dependencies: {
         'core-js': '^3.1.2'
       }
     }, true)
 
-    api.transformScript('babel.config.js', require('../codemods/usePluginPreset'))
-
     // TODO: implement a codemod to migrate polyfills
     api.exitLog(`core-js has been upgraded from v2 to v3.
 If you have any custom polyfills defined in ${chalk.yellow('babael.config.js')}, please be aware their names may have been changed.