R1:86611708191c

Fix a couple typos in "why so many databases?" document

Summary: One missing word, one `0` that should be a `)`, simplify a couple of mega-clauses to improve readability?

Test Plan: ((O)) . ((O))

Reviewers: michaeljs1990, chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D15252