40px of padding was added to the left and right of the footer widget area as the spacing between widgets was improved.
This footer widget area padding makes sure that the area had spacing when the screen size is reduced.
The reason it was causing scroll for you is because you set the footer widgets to be 100% width, so what was happening is they were 100% width + 80px (40 each side).
If you removed the 100% width CSS, you can keep the 40px of padding and all will be ok.
Hope this helps 🙂