Remove persisted docked windows

ui/views/mus/desktop_window_tree_host_mus.cc

Index: ui/views/mus/desktop_window_tree_host_mus.cc
diff --git a/ui/views/mus/desktop_window_tree_host_mus.cc b/ui/views/mus/desktop_window_tree_host_mus.cc
index 02cf6376934d0bff1123c9b9149b382b160d6280..f9fc5071018ed202cf0115773ccf6d883874fa9a 100644
--- a/ui/views/mus/desktop_window_tree_host_mus.cc
+++ b/ui/views/mus/desktop_window_tree_host_mus.cc
@@ -203,6 +203,7 @@ DesktopWindowTreeHostMus::~DesktopWindowTreeHostMus() {
 }
 
 bool DesktopWindowTreeHostMus::IsDocked() const {
+  // TODO(afakhry): Remove in M58.
   return window()->GetProperty(aura::client::kShowStateKey) ==
          ui::SHOW_STATE_DOCKED;
 }
@@ -357,6 +358,7 @@ aura::WindowTreeHost* DesktopWindowTreeHostMus::AsWindowTreeHost() {
 void DesktopWindowTreeHostMus::ShowWindowWithState(ui::WindowShowState state) {
   if (state == ui::SHOW_STATE_MAXIMIZED || state == ui::SHOW_STATE_FULLSCREEN ||
       state == ui::SHOW_STATE_DOCKED) {
+    // TODO(afakhry): Remove in M58.
     window()->SetProperty(aura::client::kShowStateKey, state);
   }
   window()->Show();