message: Fix design docs link
  When the repo became public, the design docs link changed
diff: @@ -3,7 +3,7 @@ Smithy code generators for Rust
  The nightly SDK build can be found under `Actions -> CI (take latest run) -> Artifacts`
  -[Design documentation (WIP)](https://ubiquitous-robot-7dc8d16d.pages.github.io/)
  +[Design documentation (WIP)](https://awslabs.github.io/smithy-rs/)
  **All internal and external interfaces are considered unstable and subject to change without notice.**
  