I’m actually the author of “clean embeds”, the original source is in this forum post: Meta Post - Common CSS Hacks - #411 by Moonbase59
If anything changes, I will update only this post, it’s up to the friendly people collecting this stuff on their GitHub pages to also update their copy (not always an easy task).
So always good to take a peek at the original, too. 
Glad that it could help you!