Fix a couple of lints

src/resources.rs

@@ -36,7 +36,7 @@ pub struct UiTheme {
 }
 
 impl FromWorld for UiTheme {
-  fn from_world(world: &mut World) -> Self {
+  fn from_world(_world: &mut World) -> Self {
     Self {
       pane_bg: SLATE_100.into(),
 

src/widgets/machines.rs

@@ -87,7 +87,7 @@ impl RotatingMachine {
           Pickable::default(),
         ))
         .with_children(|cmds| {
-          let button_cmds = cmds.spawn(BigRedButton::bundle("TURN"));
+          let _button_cmds = cmds.spawn(BigRedButton::bundle("TURN"));
           // TODO: Attach on-press observer to the button.
         });
     });