Remove community call notes from top-level Community page

[JasonWeill]

https://jupyter.org/community is long — if printed on 8.5 × 11" paper, it would fill 11 pages, and of that, about 7 pages are links to portions of community call notes. Some of the community calls whose notes are on the top-level Community page are years old.

Move the community call notes to a separate page, and link to that page from the Community page, please.