Failing lint check with the latest traitlets

[jtpio]

Looks like the latest traitlets causes the lint check to fail on CI:

https://github.com/jupyter/notebook/actions/runs/6377215958/job/17305469073?pr=7080

notebook/app.py:256: error: Incompatible types in assignment (expression has type "Dict[str, Any]", base class "Application" defined the type as "Dict[Union[str, Tuple[str, ...]], Tuple[Union[Dict[str, Any], Config], str]]")  [assignment]
notebook/app.py:257: error: Cannot determine type of "flags"  [has-type]
notebook/app.py:262: error: Cannot determine type of "flags"  [has-type]
notebook/app.py:267: error: Unused "type: ignore" comment  [unused-ignore]
notebook/app.py:271: error: Unused "type: ignore" comment  [unused-ignore]
notebook/app.py:275: error: Unused "type: ignore" comment  [unused-ignore]
notebook/app.py:279: error: Unused "type: ignore" comment  [unused-ignore]
notebook/app.py:283: error: Unused "type: ignore" comment  [unused-ignore]
notebook/app.py:287: error: Unused "type: ignore" comment  [unused-ignore]
notebook/app.py:291: error: Unused "type: ignore" comment  [unused-ignore]

This might be related to ipython/traitlets#868.