Add clarifying comment regarding Swift AST entries
Add clarifying comment regarding Swift AST entries

Summary: Adds a useful comment about the Swift AST paths.

Reviewed By: natestedman

shipit-source-id: e6905e80bc4bbfc2f7ec9a925745b123f15e2b19

JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck,JoelMarcey/buck