platform_impl/linux/x11: fix deadlock in fn set_fullscreen_inner (#1579)

Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

src/platform_impl/linux/x11/window.rs

@@ -640,6 +640,7 @@ impl UnownedWindow {
                 let flusher = self.set_fullscreen_hint(false);
                 let mut shared_state_lock = self.shared_state.lock();
                 if let Some(position) = shared_state_lock.restore_position.take() {
+                    drop(shared_state_lock);
                     self.set_position_inner(position.0, position.1).queue();
                 }
                 Some(flusher)