Replace RemoveWithoutPathExpansion(.*, nullptr) with Value::RemoveKey()

DictionaryValue::RemoveWithoutPathExpansion() is deprecated. For the
case where nullptr is passed for the output argument, Value::RemoveKey()
is a trivial replacement.

Mostly done with the following command line, plus a bit of finesse:
% git grep -l RemoveWithoutPathExpansion | \
  xargs sed -E -i 's/RemoveWithoutPathExpansion\((.*), nullptr/RemoveKey\(\1/g'

Bug: 646113

This CL was uploaded by git cl split.

R=fernandex@chromium.org

Change-Id: I230ddff389ed6baeede4e0e95455f8aafe68f592
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2298880
Auto-Submit: Anand K Mistry <amistry@chromium.org>
Reviewed-by: Nohemi Fernandez <fernandex@chromium.org>
Commit-Queue: Nohemi Fernandez <fernandex@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789870}

components/signin/ios/browser/account_consistency_service.mm

@@ -414,7 +414,7 @@ void AccountConsistencyService::FinishedApplyingCookieRequest(bool success) {
         break;
       case REMOVE_CHROME_CONNECTED_COOKIE:
         // Remove request.domain from prefs.
-        update->RemoveWithoutPathExpansion(request.domain, nullptr);
+        update->RemoveKey(request.domain);
         break;
     }
   }