update kotlin samples

Author: wing328

samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/apis/BirdApi.kt

@@ -112,7 +112,7 @@ class BirdApi(basePath: kotlin.String = defaultBasePath, client: OkHttpClient =
 
         return RequestConfig(
             method = RequestMethod.GET,
-            path = "/v1/bird/{id}".replace("{"+"id"+"}", "$id"),
+            path = "/v1/bird/{id}".replace("{"+"id"+"}", id.toString()),
             query = localVariableQuery,
             headers = localVariableHeaders,
             body = localVariableBody