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/Mind/Components/MindComponent.cs

@@ -3,13 +3,14 @@ namespace Content.Server.Mind.Components
     /// <summary>
     ///     Stores a <see cref="Server.Mind.Mind"/> on a mob.
     /// </summary>
-    [RegisterComponent, Friend(typeof(MindSystem))]
+    [RegisterComponent, Access(typeof(MindSystem))]
     public sealed class MindComponent : Component
     {
         /// <summary>
         ///     The mind controlling this mob. Can be null.
         /// </summary>
         [ViewVariables]
+        [Access(typeof(MindSystem), Other = AccessPermissions.ReadWriteExecute)] // FIXME Friends
         public Mind? Mind { get; set; }
 
         /// <summary>