Marked ResetAttributeDescriptors() as static

Since it doesn't work with any state data. As this is a `private` function, this doesn't affect the public API in any way, nor any calls to the function.

Author: JeremyCaney

OnTopic/Repositories/TopicRepositoryBase.cs

@@ -634,7 +634,7 @@ topic is AttributeDescriptor &&
     ///   reflected.
     /// </remarks>
     /// <param name="topic">The <see cref="Topic"/> to evaluate as an <see cref="AttributeDescriptor"/>.</param>
-    private void ResetAttributeDescriptors(Topic topic) {
+    private static void ResetAttributeDescriptors(Topic topic) {
       if (IsAttributeDescriptor(topic)) {
         ((ContentTypeDescriptor)topic.Parent!.Parent!).ResetAttributeDescriptors();
       }