Remove usage of no-op macro DEFINE_WEB_STATE_USER_DATA_KEY.

This CL removes macro usage from /ios/chrome/browser/translate.

This CL was uploaded by git cl split.

R=toyoshim@chromium.org

Bug: 589840
Change-Id: Ia199152845344221db491b895f44ea5a885046f1
Reviewed-on: https://chromium-review.googlesource.com/c/1351080Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611244}

ios/chrome/browser/translate/chrome_ios_translate_client.mm

@@ -51,8 +51,6 @@
 #error "This file requires ARC support."
 #endif
 
-DEFINE_WEB_STATE_USER_DATA_KEY(ChromeIOSTranslateClient);
-
 // static
 void ChromeIOSTranslateClient::CreateForWebState(
     web::WebState* web_state,