setup.py install_requires add ipywidgets version

[jimmybow]

ipywidgets 8 is not surport, please add version info to setup.py
ipywidgets>=7.6,<8
https://github.com/twosigma/beakerx_tabledisplay/blob/master/beakerx_tabledisplay/setup.py#L74C5-L74C21