[PR] Fix typo in type cast
[PR] Fix typo in type cast

Summary:
`:` is a colon, a semicolon would be `;`
Closes https://github.com/facebook/flow/pull/3659

Differential Revision: D4833833

Pulled By: mroch

fbshipit-source-id: dc3fb571b364f4081db78cd70b2029ec9127895a

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