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Fix typo in blog post
[docs] Move React Elements post to right place, fix typo

The URL already made its way around so we can't just break it. We might
want to just live with it instead of even doing this redirect.

https://github.com/plaxdan/react/commit/2b225446c03192b58e176f8885e60055cf5ea436#commitcomment-8176218
Merge pull request #2357 from jimjea/patch-1

Minor grammar change to Thinking in React