Index: wp-content/themes/twentyfourteen/css/blocks.css
===================================================================
--- wp-content/themes/twentyfourteen/css/blocks.css	(revision 56614)
+++ wp-content/themes/twentyfourteen/css/blocks.css	(working copy)
@@ -227,7 +227,7 @@
 
 .wp-block-table th,
 .wp-block-table td {
-	border-color: rgba(0, 0, 0, 0.1);
+	
 	border-width: 0 1px 1px 0;
 }
 
Index: wp-content/themes/twentyfourteen/style.css
===================================================================
--- wp-content/themes/twentyfourteen/style.css	(revision 56614)
+++ wp-content/themes/twentyfourteen/style.css	(working copy)
@@ -422,7 +422,7 @@
 table,
 th,
 td {
-	border: 1px solid rgba(0, 0, 0, 0.1);
+	border: 1px solid;
 }
 
 table {