Fix disabling auto-suggestions (#13914)...
Fix disabling auto-suggestions (#13914)
This should fix
#13913 but I could not reproduce it in the first place.
It looks like the traitlets initialization was invoking setter handler
before the `__init__` had time to set `auto_suggest = None`; this is now
changed so that `auto_suggest` is set to `None` on class level. It might
be not as elegant because it makes it a class variable but in fact
`pt_app` also uses the same pattern and since `auto_suggest` is only
used on `pt_app` there is no reason not to use this pattern.
Also, the type annotation was in a wrong class, I moved it.
