[FilesApp] Remove demo mode TODO

Remove "TODO(crbug.com/868747): Find a better solution for demo mode",
since 1) the better solution is unknown and 2) the current solution is
working fine.  Comment-only change.

No-try: true
Bug: 868747
Change-Id: I315fe8d9f5cba4ae35ebae35638ddac182732540
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1809026Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697902}

chrome/browser/chromeos/extensions/file_manager/private_api_strings.cc

@@ -35,7 +35,6 @@ ExtensionFunction::ResponseAction FileManagerPrivateGetStringsFunction::Run() {
   dict->SetBoolean("VIDEO_PLAYER_NATIVE_CONTROLS_ENABLED",
                    base::FeatureList::IsEnabled(
                        chromeos::features::kVideoPlayerNativeControls));
-  // TODO(crbug.com/868747): Find a better solution for demo mode.
   dict->SetBoolean("HIDE_SPACE_INFO",
                    chromeos::DemoSession::IsDeviceInDemoMode());
   dict->SetBoolean("ARC_USB_STORAGE_UI_ENABLED",