Revert "Add OutputCommand::SetPointerPosition to set mouse position" (#5867)

Reverts emilk/egui#5776

I noticed that this is already a `ViewportCommand`. Sorry for not seeing
that earlier.

crates/eframe/src/web/app_runner.rs

@@ -336,9 +336,6 @@ impl AppRunner {
                 egui::OutputCommand::OpenUrl(open_url) => {
                     super::open_url(&open_url.url, open_url.new_tab);
                 }
-                egui::OutputCommand::SetPointerPosition(_) => {
-                    // Not supported on the web.
-                }
             }
         }