[PR] Normalize `;` vs `,` in interface separators
[PR] Normalize `;` vs `,` in interface separators

Summary:
The interface docs was inconsistent, it uses `;` and `,` as separators interchangeably. This PR normalizes the entire document to use `,`, which is what prettier does and what I've seen most used in flow codebases.
Closes https://github.com/facebook/flow/pull/4951

Reviewed By: calebmer

Differential Revision: D5891977

Pulled By: vjeux

fbshipit-source-id: 01f4f88aed1a21f70a834b360fe3ca4fa7beab82

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