One of the most popular modules Divi is the one from blog style grid, or masonry which shows the last entries so that they look like in boxes stacked in aesthetically mode messy.
If you use the social network Pinterest you know what I'm talking about, it's very similar.
This module, by default, adds an additional margin and wraps the entries in boxes with border that you can remove if you want.
To eliminate that additional margin and border you just have to add the following code in section Additional CSS WordPress Personalizer .
Save the changes and you'll have the grid-style blog module, or masonry, cleaner like this: