Remove YouTube video from the README

Author: nedtwigg

README.md

@@ -16,8 +16,6 @@
 
 ![screenshot of the draft history popup](.github/screenshot-popup.png)
 
-[![screenshot of the draft history popup](.github/youtube-thumbnail.jpg)](https://www.youtube.com/watch?v=wm7fVg4DWqk)
-
 ## Contributing
 
 If there's something you'd like to add or fix, see [CONTRIBUTING.md](CONTRIBUTING.md).