Fix documentation for task registration example (#1443)

Fix documentation by correcting function name in task registration example

Co-authored-by: Itay Etelis <[email protected]>

docs/docs/adding_task.rst

@@ -89,7 +89,5 @@ To register the task to the catalog
 
    from unitxt import add_to_catalog
 
-   add_to_local_catalog(task,"tasks.calculator.sum")
-
-
+   add_to_catalog(task,"tasks.calculator.sum")