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.Server/Station/Components/StationSpawningComponent.cs

@@ -5,7 +5,7 @@ namespace Content.Server.Station.Components;
 /// <summary>
 /// Controls spawning on the given station, tracking spawners present on it.
 /// </summary>
-[RegisterComponent, Friend(typeof(StationSpawningSystem))]
+[RegisterComponent, Access(typeof(StationSpawningSystem))]
 public sealed class StationSpawningComponent : Component
 {
 }