Bars in the same `alignmentgroup` should have the same width

Followup from https://github.com/plotly/plotly.py/issues/3715 ... In this pen https://codepen.io/nicolaskruchten/pen/RwQxYJK we see that the upper subplot has a bar, but it's auto-width'ed to 1ms or something because there are no other bars in the subplot. But it's in an alignmentgroup with the traces on the other subplot so they should have the same width.