themes-wordpress/quadrat/sass/blocks/_table.scss

.wp-block-table.is-style-stripes,
.wp-block-table {
	th {
		font-weight: 400;
	}

	tbody td { // tbody adds the specificity needed to override the default Gutenberg styles
		border-bottom-width: 0;
		border-top-width: 0;
		vertical-align: top;
		border-color: var(--wp--preset--color--primary);
	}

	tr:first-child td {
		border-top-width: 1px;
	}

	tr:last-child td {
		border-bottom-width: 1px;
	}
}