remove modern mode babel target change

refs vuejs/vue-cli#5513

Author: sapphi-red

babel.config.js

@@ -1,19 +1,3 @@
-/* eslint-disable @typescript-eslint/no-var-requires */
-const vueCliPreset = require('@vue/cli-plugin-babel/preset')
-
-module.exports = api => {
-  api.cache.using(() => process.env.VUE_CLI_MODERN_BUILD)
-  api.cache.using(() => process.env.NODE_ENV)
-
-  const isModern = process.env.VUE_CLI_MODERN_BUILD === 'true'
-
-  if (isModern) {
-    delete process.env.VUE_CLI_MODERN_BUILD
-  }
-  const config = vueCliPreset(api)
-  if (isModern) {
-    process.env.VUE_CLI_MODERN_BUILD = 'true'
-  }
-
-  return config
+module.exports = {
+  presets: ['@vue/cli-plugin-babel/preset']
 }