Remove unnecessary and redundant topic.Parent setting

In the `Move()` action of the `EditorController`, the `topic.Parent` was explicitly being set to the new `target` parent. Not only is this unnecessary and redundant—since the underlying `ITopicRepository.Move()` will handle that—but it also introduces room for bugs since it will appear to `ITopicRepository` that the parent has not changed. I.e., if it compares `topic.Parent` to `target`, they will be the same, thus making it appear as a reordering, not a move. By not setting this in `EditorController`, we give `ITopicRepository` more reliable information, and centralize how this value is updated.

Author: JeremyCaney

OnTopic.Editor.AspNetCore/Controllers/EditorController.cs

@@ -491,11 +491,6 @@ public IActionResult Move(int topicId, int targetTopicId = -1, int siblingId = -
       var topic = TopicRepository.Load(topicId);
       var target = (targetTopicId >= 0)? TopicRepository.Load(targetTopicId) : topic.Parent;
 
-      /*--------------------------------------------------------------------------------------------------------------------------
-      | Reset the source topic's Parent
-      \-------------------------------------------------------------------------------------------------------------------------*/
-      topic.Parent = target;
-
       /*--------------------------------------------------------------------------------------------------------------------------
       | Move the topic and/or reorder it with its siblings; lock the Topic repository prior to execution
       \-------------------------------------------------------------------------------------------------------------------------*/