docs: Fix incorrect kscan value (zmkfirmware#2763)

Author: Aasim-A

docs/docs/development/hardware-integration/dongle.mdx

@@ -240,7 +240,7 @@ Finally, select your physical layout in the chosen node.
 ```dts
 / {
     chosen {
-        zmk,kscan = &kscan0;
+        zmk,kscan = &mock_kscan;
         zmk,physical-layout = &physical_layout0;
     };
 };