Update obsolete mention of Sequoia, now known as Tungsten

Per http://joomla.aws.continuent.com/community/lab-projects/sequoia

Greg Smith

doc/src/sgml/high-availability.sgml

@@ -210,8 +210,8 @@ protocol to make nodes agree on a serializable transactional order.
      transactions either commit or abort on all servers, perhaps
      using two-phase commit (<xref linkend="sql-prepare-transaction">
      and <xref linkend="sql-commit-prepared">.
-     <productname>Pgpool-II</> and <productname>Sequoia</> are examples of
-     this type of replication.
+     <productname>Pgpool-II</> and <productname>Continuent Tungsten</>
+     are examples of this type of replication.
     </para>
    </listitem>
   </varlistentry>