woocommerce/plugins/woocommerce-admin/client/dashboard/store-performance/style.scss

/** @format */

.woocommerce-dashboard__store-performance {
	border-bottom: 0;
	border-right: 0;

	.woocommerce-card__header {
		border-right: 1px solid $core-grey-light-700;
	}

	.woocommerce-card__body {
		padding: 0;
	}

	.woocommerce-summary {
		margin: 0;
	}
}