[css-text-3] Correct mistake in previous commit

Author: fantasai

css-text-3/Overview.bs

@@ -1097,7 +1097,7 @@ Text Processing</h3>
     </li>
     <li><p>If 'white-space' is set to ''pre'' or ''pre-wrap''
       any sequence of spaces is treated as a sequence of non-breaking spaces;
-      however, a <a>soft wrap opportunity</a> exists at the end of the sequence.
+      however, for ''pre-wrap'', a <a>soft wrap opportunity</a> exists at the end of the sequence.
       In the case of ''break-spaces'',
       a <a>soft wrap opportunity</a> exists after every space.
       <wpt>