Remove remaing from 'os' imports

Summary: Per title.

Reviewed By: passy

Differential Revision: D32721206

fbshipit-source-id: 9e465d0ed60c0c6da33c462aa76468faac620626

desktop/flipper-ui-core/src/fb-stubs/checkForUpdate.tsx

@@ -7,13 +7,13 @@
  * @format
  */
 
-import os from 'os';
 import {VersionCheckResult} from '../chrome/UpdateIndicator';
+import {getRenderHostInstance} from '../RenderHost';
 
 const updateServer = 'https://www.facebook.com/fbflipper/public/latest.json';
 
 const getPlatformSpecifier = (): string => {
-  switch (os.platform()) {
+  switch (getRenderHostInstance().serverConfig.environmentInfo.os.platform) {
     case 'win32':
       return 'windows';
     case 'linux':