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

crates/egui_demo_app/src/apps/custom3d_wgpu.rs

@@ -1,8 +1,5 @@
 use std::sync::Arc;
 
-#[cfg(target_arch = "wasm32")]
-use core::any::Any;
-
 use eframe::{
     egui_wgpu::{self, wgpu},
     wgpu::util::DeviceExt,
@@ -120,11 +117,6 @@ impl eframe::App for Custom3d {
                 });
         });
     }
-
-    #[cfg(target_arch = "wasm32")]
-    fn as_any_mut(&mut self) -> &mut dyn Any {
-        &mut *self
-    }
 }
 
 impl Custom3d {