fix: followup of jupyter-widgets/ipywidgets#1630, resolve instead of return Promise
fix: followup of jupyter-widgets/ipywidgets#1630, resolve instead of return Promise

ipython/ipywidgets,jupyter-widgets/ipywidgets,jupyter-widgets/ipywidgets,SylvainCorlay/ipywidgets,SylvainCorlay/ipywidgets,ipython/ipywidgets,ipython/ipywidgets,SylvainCorlay/ipywidgets,jupyter-widgets/ipywidgets,SylvainCorlay/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets