fix(115open):fix limit_rate save (#601)

Author: ILoveScratch2

drivers/115_open/meta.go

@@ -11,7 +11,7 @@ type Addition struct {
 	// define other
 	OrderBy        string  `json:"order_by" type:"select" options:"file_name,file_size,user_utime,file_type"`
 	OrderDirection string  `json:"order_direction" type:"select" options:"asc,desc"`
-	LimitRate      float64  `json:"limit_rate,string" type:"float" default:"1" help:"limit all api request rate ([limit]r/1s)"`
+	LimitRate      float64  `json:"limit_rate" type:"float" default:"1" help:"limit all api request rate ([limit]r/1s)"`
 	AccessToken    string  `json:"access_token" required:"true"`
 	RefreshToken   string  `json:"refresh_token" required:"true"`
 }