OBJ import: fix (remove) deprecated viewlayer handling code.

Guess that was added when layercollection of view layer could still be
edited, that is no more the case (reading code), now view layers appear
to always only have the scene's master collection, all others being
children of that one.

io_scene_obj/import_obj.py

@@ -1179,11 +1179,7 @@ def load(context,
             create_nurbs(context_nurbs, verts_loc, new_objects)
 
         view_layer = context.view_layer
-        if view_layer.collections.active:
-            collection = view_layer.collections.active.collection
-        else:
-            collection = scene.master_collection.new()
-            view_layer.collections.link(collection)
+        collection = view_layer.collections.active.collection
 
         # Create new obj
         for obj in new_objects: