[css-text-3] Update list of forbid-break UAX14 classes. #3517

Author: fantasai

css-text-3/Overview.bs

@@ -1916,7 +1916,7 @@ Line Breaking Details</h3>
     <li>Except where explicitly defined otherwise
       (e.g. for ''line-break: anywhere'' or ''overflow-wrap: anywhere'')
       line breaking behavior defined for
-      the WJ, ZW, and GL line-breaking classes in [[!UAX14]]
+      the WJ, ZW, GL, and ZWJ line-breaking classes in [[!UAX14]]
       must be honored.
 
       <wpt>