Fix a typo in the comment for blockRenderMap
Fix a typo in the comment for blockRenderMap

Summary:
FWIW, this doesn't appear to be used in any generated documentation.
Closes https://github.com/facebook/draft-js/pull/447

Differential Revision: D3441359

fbshipit-source-id: d29c6d29fdad646a965c27d09ebfaefffc7ff6df

SciMts/draft-js,SciMts/draft-js,facebook/draft-js,davidchang/draft-js,johnmpotter/draft-js,tonygentilcore/draft-js,TripleDip/draft-js,dirkholsopple/draft-js,TripleDip/draft-js,davidchang/draft-js,tonygentilcore/draft-js,johnmpotter/draft-js,dirkholsopple/draft-js