[css3-fonts] fix markup bug causing the validator to burp

Author: John Daggett

css-fonts/Fonts.html

@@ -5378,7 +5378,7 @@ <h3 id=font-language-override-prop><span class=secno>6.13 </span>Font
    element, as <a href="#language-specific-support">described above</a>:
 
   <pre>&lt;!-- Display text using S'gaw Karen specific features -->
-&ltp lang="ksw">...&lt;/p></pre>
+&lt;p lang="ksw">...&lt;/p></pre>
 
   <p>In some cases, authors may need to specify a language system that
    differs from the content language, for example due to the need to mimic