Fix -[FBCollectionInformation oneLineDescriptionFromDictionary:]
Fix -[FBCollectionInformation oneLineDescriptionFromDictionary:]

Summary: This was broken due to not using the mutable append methods.

Reviewed By: antiarchit

Differential Revision: D5774668

fbshipit-source-id: 4f05bd07f71097cee258f80b3e826ccacb7a1d8f

facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl,facebook/FBSimulatorControl