[PR] [Docs] Fix command line flag for flow-remove-types
[PR] [Docs] Fix command line flag for flow-remove-types

Summary:
Resolves #4039.
Closes https://github.com/facebook/flow/pull/4671

Differential Revision: D5720229

Pulled By: samwgoldman

fbshipit-source-id: 9f18540eba5245e25147bcc2e7406825eb431fe6

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