Remove some more unused fields

Content.Client/Popups/PopupSystem.cs

@@ -19,7 +19,6 @@ namespace Content.Client.Popups
     public class PopupSystem : SharedPopupSystem
     {
         [Dependency] private readonly IUserInterfaceManager _userInterfaceManager = default!;
-        [Dependency] private readonly IPlayerManager _playerManager = default!;
         [Dependency] private readonly IEyeManager _eyeManager = default!;
 
         private readonly List<PopupLabel> _aliveLabels = new();