MAINTAINERS_GUIDE: Replace Chief Maintainer with GOVERNANCE

[wking]

Cherry-picked from #20, because there was more discussion in today's meeting about dropping this role, but we haven't been able to move forward with #20 as a whole. Cc @caniszczyk.

Hooray institutions ;). Because GOVERNANCE.md is already making decisions with a ⅔ vote, there's no reason to appeal to the TOB (the old ⅔ vote for appeal is now sufficient for making the decision outright).

All current OCI Projects have adopted the GOVERNANCE docs (although runc has yet to actually merge them into its repository) so I think this approach is portable while the Chief Maintainer approach was not. Taking the runc maintainer subset of that vote (just to be sure the doc applies to runc):

• +7: Aleksa Sarai, Alexander Morozov, Daniel Dao, Mrunal Patel, Qiang Huang, Rohit Jnagal, Victor Marmol
• -0
• #2: Andrey Vagin, Michael Crosby

and 7/9 > ⅔.

This also avoids the strange behavior where a ⅔ vote of maintainers could approve a new maintainer, the Chief Maintainer could veto, and the same ⅔ vote could appeal that veto to the TOB. And it's nice to have a single set of rules for project-management issues, and not a five “business days” window for new maintainers one-week window for other management issues. The ten-day window for maintainer removal is now a shorter seven, but with the call for earlier private discussion I don't think it's worth special-casing just to get an extra three days.

Also:

• Remove “across the maintainers of the project”. “respect across” seemed awkward (“respect between” is closer but still not quite right). In any case, the next sentence makes it clear with “trust one another”, so I think the bit I removed was superfluous.
• Replace “depend on and trust” with “depend on”, because building trust was already mentioned in that sentence, and I don't see any semantic distiction between “depend on and trust” and “depend on”.
• Replace “make decisions” with “act”. Same meaning, fewer letters ;).
• Adjust the paragraphs I touched to the README's recommended one line per sentence.

[caniszczyk]

Thanks!