Remove usage of no-op macro DEFINE_WEB_STATE_USER_DATA_KEY.

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

This CL was uploaded by git cl split.

R=mahmadi@chromium.org

Bug: 589840
Change-Id: I84f6c6f53c27df62ebd04b6bcc88a0e27ba67833
Reviewed-on: https://chromium-review.googlesource.com/c/1351959Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611557}

ios/chrome/browser/autofill/autofill_tab_helper.mm

@@ -13,8 +13,6 @@
 #error "This file requires ARC support."
 #endif
 
-DEFINE_WEB_STATE_USER_DATA_KEY(AutofillTabHelper);
-
 AutofillTabHelper::~AutofillTabHelper() = default;
 
 // static

ios/chrome/browser/autofill/form_suggestion_tab_helper.mm

@@ -12,8 +12,6 @@
 #error "This file requires ARC support."
 #endif
 
-DEFINE_WEB_STATE_USER_DATA_KEY(FormSuggestionTabHelper);
-
 FormSuggestionTabHelper::~FormSuggestionTabHelper() = default;
 
 // static