Updated Roadmap (markdown)

Roadmap.md

@@ -11,7 +11,7 @@ This page describes a prioritized backlog of new vcpkg feature work and completi
   - [ ] **Release date:** June 2020 (2020.06)
 - [ ] **Manifest file support** 
   - [x] **Description:** Vcpkg will support a manifest file that can specify all your dependencies declaratively and can be checked into source control.
-  - [x] **Specification/design document:** [Link to draft PR](https://github.com/microsoft/vcpkg/pull/11203)
+  - [x] **Specification/design document:** [Link to spec](https://github.com/microsoft/vcpkg/blob/master/docs/specifications/manifests.md)
   - [ ] **Release date:** May 2020 (2020.05) 
 - [ ] **Package federation** 
   - [x] **Description:** Vcpkg will allow you to easily install packages from multiple sources.