serv4 + submodule update (#12740)

Co-authored-by: DrSmugleaf <DrSmugleaf@users.noreply.github.com>

Content.Server/Electrocution/ElectrocutionNode.cs

@@ -1,6 +1,5 @@
 using Content.Server.NodeContainer;
 using Content.Server.NodeContainer.Nodes;
-using Robust.Shared.Map;
 using Robust.Shared.Map.Components;
 
 namespace Content.Server.Electrocution
@@ -11,7 +10,7 @@ namespace Content.Server.Electrocution
         [DataField("cable")]
         public EntityUid CableEntity;
         [DataField("node")]
-        public string NodeName = default!;
+        public string? NodeName;
 
         public override IEnumerable<Node> GetReachableNodes(TransformComponent xform,
             EntityQuery<NodeContainerComponent> nodeQuery,