@wordpress/block-library/build-style/columns/editor.css

Block library for the WordPress editor.

.wp-block-columns :where(.wp-block) {
  max-width: none;
  margin-left: 0;
  margin-right: 0;
}

html :where(.wp-block-column) {
  margin-top: 0;
  margin-bottom: 0;
}