Fix some friend access violations by allowing others access. (#8594)

Rename Friend attribute to Access attribute.
Updates submodule to v0.21.0.0 as well.

Content.Shared/Pulling/Components/PullableComponent.cs

@@ -7,7 +7,7 @@ namespace Content.Shared.Pulling.Components
 {
     // Before you try to add another type than SharedPullingStateManagementSystem, consider the can of worms you may be opening!
     [NetworkedComponent()]
-    [Friend(typeof(SharedPullingStateManagementSystem))]
+    [Access(typeof(SharedPullingStateManagementSystem))]
     [RegisterComponent]
     public sealed class SharedPullableComponent : Component
     {
@@ -26,6 +26,7 @@ namespace Content.Shared.Pulling.Components
 
         public bool BeingPulled => Puller != null;
 
+        [Access(typeof(SharedPullingStateManagementSystem), Other = AccessPermissions.ReadExecute)] // FIXME Friends
         public EntityCoordinates? MovingTo { get; set; }
 
         public override ComponentState GetComponentState()