Make eframe::App::as_any_mut optional to implement (#2061)

crates/egui_demo_app/src/apps/custom3d_glow.rs

@@ -1,8 +1,5 @@
 use std::sync::Arc;
 
-#[cfg(target_arch = "wasm32")]
-use core::any::Any;
-
 use eframe::egui_glow;
 use egui::mutex::Mutex;
 use egui_glow::glow;
@@ -51,11 +48,6 @@ impl eframe::App for Custom3d {
             self.rotating_triangle.lock().destroy(gl);
         }
     }
-
-    #[cfg(target_arch = "wasm32")]
-    fn as_any_mut(&mut self) -> &mut dyn Any {
-        &mut *self
-    }
 }
 
 impl Custom3d {