linux/x11: Only create ModifiersChanged event if they changed (#12879)

I noticed that when I use my mouse wheel, we get a ton of the
`XkbStateNotify` events, but the modifiers don't change, so we add a ton
of useless input events for the window.

Release Notes:

- N/A

crates/gpui/src/platform/linux/x11/client.rs

@@ -524,7 +524,11 @@ impl X11Client {
                     0,
                     event.locked_group.into(),
                 );
+
                 let modifiers = Modifiers::from_xkb(&state.xkb);
+                if state.modifiers == modifiers {
+                    drop(state);
+                } else {
                     let focused_window_id = state.focused_window?;
                     state.modifiers = modifiers;
                     drop(state);
@@ -534,6 +538,7 @@ impl X11Client {
                         ModifiersChangedEvent { modifiers },
                     ));
                 }
+            }
             Event::KeyPress(event) => {
                 let window = self.get_window(event.event)?;
                 let mut state = self.0.borrow_mut();