[css-text-3] Ignore out-of-flow elements for hyphenation

Closes #3862

Author: frivoal

css-text-3/Overview.bs

@@ -2735,6 +2735,7 @@ Line Breaking Details</h3>
       <p>For the purpose of the 'hyphens' property,
       what constitutes a “word” is UA-dependent.
       However, inline element boundaries
+      and out-of-flow elements
       must be ignored when determining word boundaries.
 
       <wpt>