Same problem, but I don’t have that CSS. This just started after I switched from the Classic Widgets plugin to using the Gutenberg ones, and then removed and replaced a legacy Search widget with the new one. I’ve shrunk the search box, but it isn’t causing the first footer widget to go back to normal size.
the GP Footer uses CSS Flexbox for its grid, which allows for columns to reflow if there contents require it.
In this case you search block wants more space. You can fix its width using this CSS: