all: use expect attribute where possible

src/it/test_utils/test_expected_event.rs

@@ -17,7 +17,6 @@ impl<T> TestExpectedEvent<T> {
         }
     }
 
-    #[allow(dead_code)]
     pub fn last(&self) -> TestResult<T> {
         match self.data.events.borrow_mut().pop_back() {
             Some(t) => Ok(t),

src/it/test_utils/test_surface_ext.rs

@@ -38,7 +38,6 @@ impl TestSurfaceExt {
         Ok(())
     }
 
-    #[allow(dead_code)]
     pub fn set_color(&self, r: u8, g: u8, b: u8, a: u8) {
         self.color.set(Color::from_rgba_straight(r, g, b, a));
     }