doc: revise strategic initiatives text

Now that it's in the core repo, so ome of the TSC-centric text doesn't
make as much sense as it did when it was in the TSC repo.

PR-URL: https://github.com/nodejs/node/pull/39417


Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>