Replace CanBeNull annotations with nullable reference types (#1270)

Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Content.Server/GameObjects/Components/Access/AccessComponent.cs

@@ -1,11 +1,10 @@
+#nullable enable
 using System.Collections.Generic;
 using Content.Server.Interfaces;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
 
-#nullable enable
-
 namespace Content.Server.GameObjects.Components.Access
 {
     /// <summary>