Basically it is not possible to remove such hard coded subtitles from the video.
The only way is to use dirty tricks like blurring them, or covering it with a gray bar or so. But that's a whole different story. On the forum of videohelp.com you may find some more info on this, for example this post:
https://forum.videohelp.com/threads/358 ... ELP-PLEASE
You may be better off trying to find a video version without hard coded subs.