Remove internal comment (#830)

Author: Larah Armstrong

docs/api/Unity.Netcode.NetworkBehaviour.md

@@ -304,17 +304,7 @@ public NetworkManager NetworkManager { get; }
 #### NetworkObject
 
 
-Gets the NetworkObject that owns this NetworkBehaviour instance TODO:
-this needs an overhaul. It's expensive, it's ja little naive in how it
-looks for networkObject in its parent and worst, it creates a puzzle if
-you are a NetworkBehaviour wanting to see if you're live or not (e.g.
-editor code). All you want to do is find out if NetworkManager is null,
-but to do that you need NetworkObject, but if you try and grab
-NetworkObject and NetworkManager isn't up you'll get the warning below.
-This is why IsBehaviourEditable had to be created. Matt was going to
-re-do how NetworkObject works but it was close to the release and too
-risky to change
-
+Gets the NetworkObject that owns this NetworkBehaviour instance.