Remove unused `ThreadingHelpers`.
DELETE
WalletWasabi/Helpers/ThreadingHelpers.cs
-namespace System.Threading
-{
- public static class ThreadingHelpers
- {
- public static CancellationToken Cancelled
- {
- get
- {
- if (!CancelledBacking.HasValue)
- {
- using var cts = new CancellationTokenSource();
- cts.Cancel();
- CancelledBacking = cts.Token;
- }
- return CancelledBacking.Value;
- }
- }
-
- private static CancellationToken? CancelledBacking { get; set; } = null;
- }
-}

Remove unused `ThreadingHelpers`.