chore: remove references to plugin sdk ARCHITECTURE.md

plugins/serial/README.md

@@ -10,7 +10,7 @@ Open a serial console to a device plugged into your computer.
 
 ## Setup
 
-The desktop app uses the `serialport` npm package, which has a native binary. The build does not bundle it. See "native dependencies" in `packages/plugin-sdk/ARCHITECTURE.md` for how Docker, Electron and dev each get a working copy.
+The desktop app uses the `serialport` npm package, which has a native binary. The build does not bundle it.
 
 ## Development
 
@@ -19,5 +19,3 @@ npm run build      # build into dist/
 npm run test       # run this plugin's tests
 npm run typecheck  # type-check this plugin
 ```
-
-See `packages/plugin-sdk/ARCHITECTURE.md` for the plugin contract.