distplot deprecation warning

[jreadey]

Several cells in the 04-WTK_NSRDB-comparison.ipynb notebook gives a deprecation warning.

`distplot` is a deprecated function and will be removed in seaborn v0.14.0.

Please adapt your code to use either `displot` (a figure-level function with
similar flexibility) or `histplot` (an axes-level function for histograms).

For a guide to updating your code to use the new functions, please see
https://gist.github.com/mwaskom/de44147ed2974457ad6372750bbe5751

It would be great to fix this before 0.14.0 comes around.