ipyannotations.text.MulticlassLabeller ignores `max_buttons`

[mawicks]

The max_buttons parameter in the following sample code does not produce the intended effect. It doesn't appear that max_buttons is even referenced in generic.MulticlassLabeller:

import ipyannotations.text

widget = ipyannotations.text.MulticlassLabeller(
    options=range(30),
    max_buttons=3
)
widget.display("Greetings!")
widget