Change references to Executive Council to Board of Directors

[froggleston]

How could the content be improved?

As the Executive Council no longer exists and is replaced by the Board of Directors, references to the EC should be replaced with descriptions and links to the new information: https://carpentries.org/governance/

Which part of the content does your suggestion apply to?

https://carpentries.github.io/instructor-training/instructor/15-carpentries.html

[brownsarahm]

@kariljordan while we are in the transition period and have two bodies, should we explain the currents status or the future model? Should we wait and revise to BoD when the transition is complete?

[kariljordan]

Great ping @brownsarahm!

On our governance page we explain it this way, and I believe this may be the best language to include in a pargraph either immediately before or after the figure of the very brief history of our organization.

**The Carpentries is a fiscally sponsored project of Community Initiatives, a registered 501(c)(3) non-profit based in California, USA. The Carpentries is transitioning out of fiscal sponsorship to an independent 501(c)(3) non-profit organisation. For that reason, the organisation has two governing bodies: an Advisory Committee and a Board of Directors.

Governance of The Carpentries (a fiscally sponsored project of Community Initiatives) is undertaken by a three-person Advisory Committee.**

I'd be happy to submit a PR with my recommendation if that helps. We also have a revision of that figure we could replace the current one with. Let me know.

[brownsarahm]

a PR would be great.

[kariljordan]

#1689 is ready