Xarray logo missing on several pages

[brian-rose]

The Xarray logo has gone missing in at least these two places:

• https://foundations.projectpythia.org/core/xarray.html
• https://foundations.projectpythia.org/core/xarray/xarray-intro.html

Our source files link to the logo at http://xarray.pydata.org/en/stable/_static/dataset-diagram-logo.png but it is no longer there.

I found a current Xarray logo here instead: https://docs.xarray.dev/en/stable/_static/Xarray_Logo_RGB_Final.svg