[cr144] ActorKeyedService::StopTask takes an enum

This used to be a bool, but now it has been improved into an enum.

Chromium changes:
https://chromium.googlesource.com/chromium/src/+/adfa72255216f1ffad175697717421c27f9dca36

commit adfa72255216f1ffad175697717421c27f9dca36
Author: chrstne <chrstne@google.com>
Date:   Wed Nov 5 07:50:53 2025 -0800

    Pipe Failed state to Actor Task

    This will be rebase and submitted after
    https://chromium-review.googlesource.com/c/chromium/src/+/7113019

    Bug: 453997100, 453724281
    Change-Id: I511519a0c1f9760e309ba6e46d899f40c42f4bbb
    Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7118220
    Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
    Reviewed-by: Kevin Graney <kmg@google.com>
    Reviewed-by: Erik Chen <erikchen@chromium.org>
    Commit-Queue: Christine Ying <chrstne@google.com>
    Cr-Commit-Position: refs/heads/main@{#1540641}

Author: cdesouza-chromium

browser/ai_chat/content_agent_tool_provider.cc

@@ -82,7 +82,8 @@ std::vector<base::WeakPtr<Tool>> ContentAgentToolProvider::GetTools() {
 void ContentAgentToolProvider::StopAllTasks() {
   if (!task_id_.is_null()) {
     // `success` sets whether the task ends as state kFinished or kCancelled
-    actor_service_->StopTask(task_id_, true /* success */);
+    actor_service_->StopTask(task_id_,
+                             actor::ActorTask::StoppedReason::kTaskComplete);
   }
 }