Loosen LGTM requirements for docs

This PR, based on discussion with Solomon and the docs maintainers, loosens the LGTM requirements for docs PRs to require only two approvals from docs maintainers and one approval from the maintainers of the component(s) being documented.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)