message: Release process: fix broken link to Guix building docs
diff: @@ -118,7 +118,7 @@ details.
  ### Build and attest to build outputs:
  Follow the relevant Guix README.md sections:
  -- [Performing a build](/contrib/guix/README.md#performing-a-build)
  +- [Building](/contrib/guix/README.md#building)
  - [Attesting to build outputs](/contrib/guix/README.md#attesting-to-build-outputs)
  ### Verify other builders' signatures to your own. (Optional)
  