message: fix(preset-umi): babel build faild if react<17
diff: @@ -10,6 +10,8 @@ export async function getBabelOpts(opts: { api: IApi }) {
  presetEnv: {},
  presetReact: {
  runtime: isGTEReact17 ? 'automatic' : 'classic',
  + // importSource cannot be set when runtime is classic
  + ...(isGTEReact17 ? {} : { importSource: undefined }),
  },
  presetTypeScript: {},
  pluginTransformRuntime: {},
  