default folder for "find_missing" script

[AlvaroCavalcante]

The default folder configured in the "find_missing.py" is the "videos", which only contains some samples of the downloaded videos. I realized that after I ran the script and get almost 21k lines in the missing.txt.

It doesn't make more sense to change this to raw_videos or raw_videos_mp4?

[dxli94]

Thanks for raising this.

I will fix this up later accordingly,