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.Client/Explosion/TriggerOnProximityComponent.cs

@@ -2,5 +2,5 @@ using Content.Shared.Explosion;
 
 namespace Content.Client.Explosion;
 
-[RegisterComponent, Friend(typeof(TriggerSystem))]
+[RegisterComponent, Access(typeof(TriggerSystem))]
 public sealed class TriggerOnProximityComponent : SharedTriggerOnProximityComponent {}