[css-ui-4] Remove stray text

Author: frivoal

css-ui-4/Overview.bs

@@ -484,7 +484,6 @@ having it overlap other text by default.
 If there is insufficient space for both start
 and end ellipses/strings,
 then only the end ellipsis/string should be rendered.
-	Issue: Add final level 3 content
 
 <dl dfn-type=value dfn-for=text-overflow>
 </dl>