Remove Contextual Suggestions preferences from incognito whitelist.

Contextual Suggestions preferences are removed from the persistent
storage list for incognito mode.
After this CL, if this preference is changed from incognito mode,
it is only stored in memory and won't affect user profile.

Bug: 861722
Change-Id: Ia1c68e786c3509905391651c9a95cf2d152bf5ea
Reviewed-on: https://chromium-review.googlesource.com/1174117Reviewed-by: Filip Gorski <fgorski@chromium.org>
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583176}

chrome/browser/prefs/pref_service_incognito_whitelist.cc

@@ -32,7 +32,6 @@
 #include "services/preferences/public/cpp/tracked/pref_names.h"
 
 #if defined(OS_ANDROID)
-#include "chrome/browser/android/contextual_suggestions/contextual_suggestions_prefs.h"
 #include "components/feed/buildflags.h"
 #include "components/feed/core/pref_names.h"
 #endif  // defined(OS_ANDROID)
@@ -187,11 +186,6 @@ const char* const kTemporaryIncognitoWhitelist[] = {
     kAnimationPolicyAllowed, kAnimationPolicyOnce, kAnimationPolicyNone,
 #endif  // !defined(OS_ANDROID)
 
-// chrome/browser/android/contextual_suggestions/contextual_suggestions_prefs.h
-#if defined(OS_ANDROID)
-    contextual_suggestions::prefs::kContextualSuggestionsEnabled,
-#endif  // defined(OS_ANDROID)
-
     // chrome/common/pref_names.h
     prefs::kAbusiveExperienceInterventionEnforce,
     prefs::kChildAccountStatusKnown, prefs::kDefaultApps,