Core file is change not recommended, it will be overwritten everytime you update this plugin.
New version will be released next week, There are so many changes in this shortcode and notification in this version. You can pass parameter to hide bracket. See https://github.com/shamim2883/front-end-pm/commit/5ea77e5c6e38c3b9a06cf45b0c4c00ce757d6030