Ticket #50180: 50180.patch

src/wp-content/themes/twentysixteen/css/blocks.css

@@ -200 +200 @@
 .wp-block-table {
         border-collapse: separate;
         border-spacing: 0;
-        border-width: 1px 0 0 1px;
+        border-width: 0;
         margin: 0 0 1.75em;
         table-layout: fixed;
         width: 100%;