XEP-0278: fix incorrect version number

xep-0278.xml

@@ -35,7 +35,7 @@
       <jid>barata7@gmail.com</jid>
     </author>
     <revision>
-      <version>0.2</version>
+      <version>0.3</version>
       <date>2017-09-14</date>
       <initials>tc</initials>
       <remark><p>Added TURN Credentials Service Support.</p></remark>