Address comments

Signed-off-by: Federico Valeri <fedevaleri@gmail.com>

Author: fvaleri

docs/upgrade.html

@@ -35,7 +35,7 @@ <h5><a id="upgrade_420_notable" href="#upgrade_420_notable">Notable changes in 4
         For further details, please refer to <a href="https://cwiki.apache.org/confluence/x/1gq9F">KIP-1157</a>.
     </li>
     <li>
-        The support for MX4J library, enabled through <code>kafka_mx4jenable</code> system property, was deprecated and will be removed in the next  major release.
+        The support for MX4J library, enabled through <code>kafka_mx4jenable</code> system property, was deprecated and will be removed in the next major release.
     </li>
 </ul>