Errors/Time visualizations break when using Seaborn 0.11

Pip now installs Seaborn 0.11 by default. Our code to visualize transfer errors over time does not work as intented with this new version (see attached side-by-side screenshot between 0.10.1 and 0.11.0).

I had a quick look at https://seaborn.pydata.org/whatsnew.html to work out why, and noticed the new Seaborn version also adds a ecdf plot: https://seaborn.pydata.org/generated/seaborn.ecdfplot.html#seaborn.ecdfplot We might consider using this to plot our ecdfs, and require Seaborn >= 0.11.0

Happy to make both these changes as part of this ticket.