[DOCS] Fix boolean for native connectors (elastic#116394) (elastic#11…

…6396)

(cherry picked from commit 22c55fa)

docs/reference/connector/docs/_connectors-create-native.asciidoc

@@ -22,7 +22,7 @@ PUT _connector/my-{service-name-stub}-connector
   "index_name": "my-elasticsearch-index",
   "name": "Content synced from {service-name}",
   "service_type": "{service-name-stub}",
-  "is_native": "true"
+  "is_native": true
 }
 ----
 // TEST[skip:can't test in isolation]