wayland not call check_get_displays_changed_msg (#8637)

* wayland not call check_get_displays_changed_msg

For wayland, call Display::all() in video service will cause block, I
don't know the reason.

Signed-off-by: 21pages <sunboeasy@gmail.com>

* Update display_service.rs

---------

Signed-off-by: 21pages <sunboeasy@gmail.com>
Co-authored-by: RustDesk <71636191+rustdesk@users.noreply.github.com>

libs/scrap/src/common/linux.rs

@@ -59,6 +59,7 @@ impl Display {
         })
     }
 
+    // Call this function carefully for wayland, it may cause blocking
     pub fn all() -> io::Result<Vec<Display>> {
         Ok(if super::is_x11() {
             x11::Display::all()?