Remove usages of AnchoredChangedMessage.

It was a component message which is now deprecated.

Content.Server/GameObjects/EntitySystems/ContainmentFieldGeneratorSystem.cs

@@ -0,0 +1,30 @@
+using Content.Server.GameObjects.Components.Singularity;
+using Robust.Shared.GameObjects;
+
+namespace Content.Server.GameObjects.EntitySystems
+{
+    public sealed class ContainmentFieldGeneratorSystem : EntitySystem
+    {
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            SubscribeLocalEvent<ContainmentFieldGeneratorComponent, PhysicsBodyTypeChangedEvent>(BodyTypeChanged);
+        }
+
+        public override void Shutdown()
+        {
+            base.Shutdown();
+
+            UnsubscribeLocalEvent<ContainmentFieldGeneratorComponent, PhysicsBodyTypeChangedEvent>();
+        }
+
+        private static void BodyTypeChanged(
+            EntityUid uid,
+            ContainmentFieldGeneratorComponent component,
+            PhysicsBodyTypeChangedEvent args)
+        {
+            component.OnAnchoredChanged();
+        }
+    }
+}