- Possible small fix for .prune ratelimiting

- Use .WhenAll extension instead of Task.WhenAll in a few more places

src/NadekoBot/Modules/Administration/Prune/PruneService.cs

@@ -46,7 +46,7 @@ public class PruneService : INService
                     await Task.WhenAll(Task.Delay(1000), channel.DeleteMessagesAsync(bulkDeletable));
 
                 foreach (var group in singleDeletable.Chunk(5))
-                    await Task.WhenAll(Task.Delay(1000), group.Select(x => x.DeleteAsync()).WhenAll());
+                    await Task.WhenAll(Task.Delay(5000), group.Select(x => x.DeleteAsync()).WhenAll());
 
                 //this isn't good, because this still work as if i want to remove only specific user's messages from the last
                 //100 messages, Maybe this needs to be reduced by msgs.Length instead of 100

src/NadekoBot/Modules/Administration/Self/SelfService.cs

@@ -170,14 +170,14 @@ public sealed class SelfService : ILateExecutor, IReadyExecutor, INService
 
     private async Task LoadOwnerChannels()
     {
-        var channels = await Task.WhenAll(_creds.OwnerIds.Select(id =>
+        var channels = await _creds.OwnerIds.Select(id =>
         {
             var user = _client.GetUser(id);
             if (user is null)
                 return Task.FromResult<IDMChannel>(null);
 
             return user.CreateDMChannelAsync();
-        }));
+        }).WhenAll();
 
         ownerChannels = channels.Where(x => x is not null)
                                 .ToDictionary(x => x.Recipient.Id, x => x)