how to remove black border around the recorded video?

[suchit-distro]

I am using code to record html-css animation video. The output video is recorded with black border around. How to get rid of this border. I tried to change the height and width in export.js but not worked.
Attached zip with webm file and screenshot showing black border
recorded_video_with_black_border.zip

[shubham-pixelnx]

This issue is already posted by me Link to that issue