wl_backend: fix shadowed sx/sy in wl_update_pointer_focus

The inner 'double sx, sy' declaration shadowed the outer one. When
view_surface_at succeeded inside the frame_buf check, the surface-local
coordinates were written to the inner variables and lost. The outer
sx/sy (used by wlr_seat_pointer_notify_enter/motion) remained
uninitialized, causing the client to receive garbage coordinates.

Also removed debug print from wclient_wl.c.

src/backend/wayland/wl_backend.c

@@ -5852,7 +5852,6 @@ wl_update_pointer_focus(uint32_t time_msec)
     if (fb) {
         /* Check if this frame_buf has a client surface (toplevel view)
          * and the pointer is over the client area, not the decorations. */
-        double sx, sy;
         struct wl_toplevel_view *v = NULL;
         struct wlr_surface *cs = view_surface_at(
             wl_state.pointer_x, wl_state.pointer_y, &sx, &sy, &v);