[Cleanup] Remove some expired omnibox field trials.

ios/chrome/browser/ios_chrome_field_trials.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ios/chrome/browser/ios_chrome_field_trials.h"
 
 #include "base/metrics/field_trial.h"
-#include "components/omnibox/browser/omnibox_field_trial.h"
 
-namespace {
-
-// Instantiates dynamic field trials by querying their state to ensure they
-// get reported as used.
-void InstantiateDynamicTrials() {
-  // Activate the autocomplete dynamic field trials.
-  OmniboxFieldTrial::ActivateDynamicTrials();
-
+void SetupFieldTrials(const base::CommandLine& command_line,
+                      const base::Time& install_time) {
   // Activate the iOS tab eviction dynamic field trials.
   base::FieldTrialList::FindValue("TabEviction");
 }
-
-}  // namespace
-
-void SetupFieldTrials(const base::CommandLine& command_line,
-                      const base::Time& install_time) {
-  InstantiateDynamicTrials();
-}