Revert "warnings: Remove ContextMessageReference when context message is deleted"

[Erisa]

Reverts #360

Reverting due to NREs

[2026-06-21 09:14:52 +00:00] [Error] Event handler exception for event "DSharpPlus.EventArgs.MessageDeletedEventArgs" thrown from "System.Threading.Tasks.Task <CanonicalizeSimpleDelegateHandler>b__0(DSharpPlus.DiscordClient, DSharpPlus.EventArgs.DiscordEventArgs, System.IServiceProvider)" (defined in "DSharpPlus.EventHandlerCollection+<>c__DisplayClass8_0").
System.NullReferenceException: Object reference not set to an instance of an object.
   at Cliptok.Events.MessageEvent.MessageDeleted(DiscordClient client, MessageDeletedEventArgs e) in /app/Events/MessageEvent.cs:line 120
   at DSharpPlus.Clients.DefaultEventDispatcher.<>c__DisplayClass9_1`1.<<DispatchAsync>b__1>d.MoveNext()