Remove unused dependencies (#19490)

Content.Server/Radio/EntitySystems/RadioSystem.cs

@@ -27,7 +27,6 @@ public sealed class RadioSystem : EntitySystem
     [Dependency] private readonly IReplayRecordingManager _replay = default!;
     [Dependency] private readonly IAdminLogManager _adminLogger = default!;
     [Dependency] private readonly IRobustRandom _random = default!;
-    [Dependency] private readonly PopupSystem _popup = default!;
     [Dependency] private readonly ChatSystem _chat = default!;
 
     // set used to prevent radio feedback loops.