Don't install console panic hook and tracing wasm subscriber in egui_web (#1230)

Do so in egui_demo_app instead

egui_web/src/backend.rs

@@ -281,12 +281,6 @@ impl AppRunner {
 /// Install event listeners to register different input events
 /// and start running the given app.
 pub fn start(canvas_id: &str, app: Box<dyn epi::App>) -> Result<AppRunnerRef, JsValue> {
-    // Make sure panics are logged using `console.error`.
-    console_error_panic_hook::set_once();
-
-    // Redirect tracing to console.log and friends:
-    tracing_wasm::set_as_global_default();
-
     let mut runner = AppRunner::new(canvas_id, app)?;
     runner.warm_up()?;
     start_runner(runner)