fix(shields): Make settings_reset more flexible.

* Don't reference `pro_micro` nexus node in settings_reset
  so it can be used with other controllers.
* Use mock kscan node instead.

app/boards/shields/settings_reset/settings_reset.keymap

@@ -12,9 +12,7 @@
         compatible = "zmk,keymap";
 
         default_layer {
-            bindings = <
-    &sys_reset
-            >;
+            bindings = <&sys_reset>;
         };
     };
 };