Qt ListStrEditor and TabularEditor setx methods use non existing _no_notify attribute

Instead of `_no_notify` this should use `_no_update`, which is the attribute used elsewhere in the editor to prevent updates.

https://github.com/enthought/traitsui/blob/835ed3516def0e961d437e43f36c033ba3a00cb1/traitsui/qt4/list_str_editor.py#L238-L247

Start with the linked section of traitsui/qt4/list_str_editor.py and locate the Qt ListStrEditor and TabularEditor setx methods. Verify that both refer to the editor attribute used elsewhere to prevent updates, then run the relevant editor tests to confirm the methods no longer reference a nonexistent attribute.

Written by the indexing model from the issue text.