Remove usages of AnchoredChangedMessage.

It was a component message which is now deprecated.

Content.Server/GameObjects/EntitySystems/GasCanisterSystem.cs

@@ -7,6 +7,28 @@ namespace Content.Server.GameObjects.EntitySystems
     [UsedImplicitly]
     internal sealed class GasCanisterSystem : EntitySystem
     {
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            SubscribeLocalEvent<GasCanisterComponent, PhysicsBodyTypeChangedEvent>(OnBodyTypeChanged);
+        }
+
+        public override void Shutdown()
+        {
+            base.Shutdown();
+
+            UnsubscribeLocalEvent<GasCanisterComponent, PhysicsBodyTypeChangedEvent>();
+        }
+
+        private static void OnBodyTypeChanged(
+            EntityUid uid,
+            GasCanisterComponent component,
+            PhysicsBodyTypeChangedEvent args)
+        {
+            component.AnchorUpdate();
+        }
+
         public override void Update(float frameTime)
         {
             foreach (var component in ComponentManager.EntityQuery<GasCanisterComponent>(true))