fix cli public api link

Author: MattSkala

public-api/README.md

@@ -22,6 +22,6 @@ This RFC is organized by chapters described on the *Table of contents* section.
 
 ## API
 
-- [CLI](./CLI)
+- [CLI](./cli)
 - [HTTP](./http)
 - [Core API (aka using IPFS as a package/module)](./core)