[docs] Remove Herald rule section from docs

Summary: The team has grown large enough now that this Herald rule is too noisy. This closes ENG-1055.

Test Plan: N/A

Reviewers: benschac, atul

Reviewed By: atul

Subscribers: palys-swm, Adrian, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3994