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=apotapchuk@chromium.org

Change-Id: I3ab03d08aae2f344e9a59057b5e3a70cb82cb6d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2298839
Auto-Submit: Anand K Mistry <amistry@chromium.org>
Reviewed-by: Anatoliy Potapchuk <apotapchuk@chromium.org>
Commit-Queue: Anatoliy Potapchuk <apotapchuk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789395}

chrome/browser/chromeos/app_mode/kiosk_cryptohome_remover.cc

@@ -43,7 +43,7 @@ void UnscheduleDelayedCryptohomeRemoval(const cryptohome::Identification& id) {
   {
     DictionaryPrefUpdate dict_update(local_state,
                                      prefs::kAllKioskUsersToRemove);
-    dict_update->RemoveWithoutPathExpansion(id.id(), nullptr);
+    dict_update->RemoveKey(id.id());
   }
   local_state->CommitPendingWrite();
 }