Update jupyter.org website to move NumFOCUS mentions to LF Charities

[jasongrout]

See mentions here

The bottom of https://jupyter.org/about (https://github.com/jupyter/jupyter.github.io/blob/4c47071864373b077a2acb5b19e7030f56731e23/about.html#L583) points to NumFOCUS for donations, so we need to update that to point to LF Charities (and mention https://jupyterfoundation.org for corporations that want to go that route).

We also have a mention on https://github.com/jupyter/jupyter.github.io/blob/4c47071864373b077a2acb5b19e7030f56731e23/privacy.md

[jasongrout]

I made a PR at jupyter/jupyter.github.io#772

[jasongrout]

We've now merged these changes are they are live, so we're done with this task.