(#494) Don't trigger SourcesUpdated messages

With the FileSystemWatcher, we don't need to manually tell Chocolatey
GUI to update the sources, as they'll be updated by the
FileSystemWatcher. Leaving them in results in duplicated entries that we
don't want.

Source/ChocolateyGui.Common.Windows/ViewModels/SettingsViewModel.cs

@@ -453,7 +453,6 @@ public async Task Save()
                 }
 
                 _originalId = DraftSource?.Id;
-                await _eventAggregator.PublishOnUIThreadAsync(new SourcesUpdatedMessage());
             }
             catch (UnauthorizedAccessException)
             {
@@ -486,7 +485,6 @@ public async Task Remove()
                     await _chocolateyService.RemoveSource(_originalId);
                     Sources.Remove(SelectedSource);
                     SelectedSource = null;
-                    await _eventAggregator.PublishOnUIThreadAsync(new SourcesUpdatedMessage());
                 }
                 catch (UnauthorizedAccessException)
                 {