Remove "webrtc_event_log_manager_remote.cc(546)] Unknown |browser_context_id|"

This is not really an error; it happens quite naturally if the user
profile has not enabled remote logging.

Bug: 1098331
Change-Id: Ia4393ff5ac42e8e3b6ddaaa3ab08a39e75e8ebb8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2260875
Commit-Queue: Elad Alon <eladalon@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782050}

chrome/browser/media/webrtc/webrtc_event_log_manager_remote.cc

@@ -543,7 +543,8 @@ void WebRtcRemoteEventLogManager::GetHistory(
   std::vector<UploadList::UploadInfo> history;
 
   if (!BrowserContextEnabled(browser_context_id)) {
-    LOG(ERROR) << "Unknown |browser_context_id|.";
+    // Either the browser context is unknown, or more likely, it's not
+    // enabled for remote logging.
     content::GetUIThreadTaskRunner({})->PostTask(
         FROM_HERE, base::BindOnce(std::move(reply), history));
     return;