Summary:
dont -> don't
refered -> referred

This is a re-run of PR#7785 and acc9679c since these typos keep coming back.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9653

Reviewed By: jay-zhuang

Differential Revision: D34879593

fbshipit-source-id: d7631fb779ea0129beae92abfb838038e60790f8