Remove dead Torznab presets

(cherry picked from commit 3454f1c9ed11fbb9aa66e16524a529e924e5a77e)

Closes #4427

src/NzbDrone.Core/Indexers/Torznab/TorznabSettings.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using System.Text.RegularExpressions;
 using FluentValidation;
@@ -10,10 +11,7 @@ namespace NzbDrone.Core.Indexers.Torznab
 {
     public class TorznabSettingsValidator : AbstractValidator<TorznabSettings>
     {
-        private static readonly string[] ApiKeyWhiteList =
-        {
-            "hd4free.xyz",
-        };
+        private static readonly string[] ApiKeyWhiteList = Array.Empty<string>();
 
         private static bool ShouldHaveApiKey(TorznabSettings settings)
         {