Minor dependency and variable cleanup. (#36730)

removal of misc unused or extra dependency definitions.

Content.Client/RCD/RCDConstructionGhostSystem.cs

@@ -13,7 +13,6 @@ namespace Content.Client.RCD;
 public sealed class RCDConstructionGhostSystem : EntitySystem
 {
     [Dependency] private readonly IPlayerManager _playerManager = default!;
-    [Dependency] private readonly RCDSystem _rcdSystem = default!;
     [Dependency] private readonly IPlacementManager _placementManager = default!;
     [Dependency] private readonly IPrototypeManager _protoManager = default!;