Adds the link to webkit bug (#52059)

Added the link to https://bugs.webkit.org/show_bug.cgi?id=291728

Author: karlcow

Diff for: css/css-tables/collapsed-border-remove-row-group.html

@@ -5,6 +5,7 @@
 <link rel="author" href="https://mozilla.org" title="Mozilla">
 <link rel="help" href="https://drafts.csswg.org/css-tables/#border-collapse-property">
 <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1907289">
+<link rel="help" href="https://bugs.webkit.org/show_bug.cgi?id=291728">
 <link rel="match" href="collapsed-border-remove-row-group-ref.html">
 <style>
   table {