Updated ipywidgets tab

According to the newest ipywidgets release - https://ipywidgets.readthedocs.io/en/8.0.2/examples/Widget%20List.html?highlight=tab#Accordion,-Tab,-and-Stack-use-selected_index,-not-value - the way to define the tabs' names is slightly different:

tab_contents = ['P0', 'P1', 'P2', 'P3', 'P4']
children = [widgets.Text(description=name) for name in tab_contents]
tab = widgets.Tab()
tab.children = children
tab.titles = [str(i) for i in range(len(children))]
tab

With this MR the expert app is updated and the pipeline fixed. Removed the restriction for the ipympl version to install.