doc: reduce repetitiveness on Consensus Seeking

Rearrange Consensus Seeking section to reduce repetitiveness.

Ref: https://github.com/nodejs/node/pull/34639#discussion_r466447930
Ref: https://github.com/nodejs/node/pull/34639#discussion_r466450850

PR-URL: https://github.com/nodejs/node/pull/34702


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>