Prune commentary and stale Rust port notes

examples/tabs/main.rs

@@ -5,10 +5,6 @@ fn main() {
     DefaultApp::<Client>::run();
 }
 
-/// The tabs example: five demo panes plus a message composer, built by
-/// `tabs_ui::build` and driven here through the winit backend. The same
-/// widget tree also runs on the android-view backend, through
-/// `iris-android-app` -- see RUST.md's I2.
 #[derive(DefaultUiState)]
 pub struct Client {
     ui_state: DefaultUiState,