[css-pseudo] Markup fix

Author: frivoal

css-pseudo/Overview.bs

@@ -240,6 +240,7 @@ The ::first-letter pseudo-element</h3>
   both letters should be considered within the ''::first-letter'' pseudo-element. [[UAX29]]
   The UA should tailor its definition of <i>typographic letter unit</i>
   to reflect the first-letter traditions of the <i>originating element</i>’s content language.
+
   Issue: This is actually a problem in cases where the originating element is an ancestor
   with a different content. What <em>should</em> we say here?