[PR] fixes a grammatical error
[PR] fixes a grammatical error

Summary: Closes https://github.com/facebook/flow/pull/3701

Differential Revision: D4868173

Pulled By: nmote

fbshipit-source-id: b75c8ba8856736e1b2ef1d29319886c1e9cd5923

jamesgpearce/flow,mroch/flow,nmote/flow,nmote/flow,claudiopro/flow,fletcherw/flow,jamesgpearce/flow,mroch/flow,mroch/flow,JonathanUsername/flow,gabelevi/flow,MichaelDeBoey/flow,facebook/flow,samwgoldman/flow,claudiopro/flow,AgentME/flow,JonathanUsername/flow,nmote/flow,AgentME/flow,mroch/flow,JonathanUsername/flow,samwgoldman/flow,TiddoLangerak/flow,jamesgpearce/flow,ylu1317/flow,samwgoldman/flow,fletcherw/flow,mroch/flow,jamesgpearce/flow,popham/flow,ylu1317/flow,fletcherw/flow,popham/flow,JonathanUsername/flow,claudiopro/flow,popham/flow,mroch/flow,facebook/flow,jamesgpearce/flow,gabelevi/flow,fletcherw/flow,JonathanUsername/flow,TiddoLangerak/flow,nmote/flow,gabelevi/flow,jamesgpearce/flow,TiddoLangerak/flow,nmote/flow,popham/flow,JonathanUsername/flow,MichaelDeBoey/flow,popham/flow,nmote/flow,JonathanUsername/flow,facebook/flow,claudiopro/flow,facebook/flow,samwgoldman/flow,ylu1317/flow,MichaelDeBoey/flow,nmote/flow,TiddoLangerak/flow,samwgoldman/flow,gabelevi/flow,jamesgpearce/flow,AgentME/flow,MichaelDeBoey/flow,fletcherw/flow,ylu1317/flow,AgentME/flow,gabelevi/flow,facebook/flow,gabelevi/flow,mroch/flow,TiddoLangerak/flow,AgentME/flow,samwgoldman/flow,claudiopro/flow,popham/flow,fletcherw/flow,samwgoldman/flow,facebook/flow,facebook/flow,ylu1317/flow,MichaelDeBoey/flow,popham/flow,gabelevi/flow