[sonic-feature.yang] fix check_up_status field type (sonic-net#10986)

- Why I did it
An issue is encountered when a value "False" is written for a feature in "check_up_status" field, which does not pass YANG validation.

- How I did it
We usually use stypes::boolean_type for such fields, even in this YANG model. This custom type, supports "False" value.

- How to verify it
Write "False" in "check_up_status" field and see if YANG validation passes.

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

src/sonic-yang-models/yang-models/sonic-feature.yang

@@ -90,8 +90,8 @@ module sonic-feature{
                 leaf check_up_status {
                     description "This configuration controls the system ready tool to check
                         the app ready/up status";
-                    type boolean;
-                    default false;
+                    type stypes:boolean_type;
+                    default "false";
                 }
             }
         }