DOC: fix sgml tags in config.sgml

Author: Liudmila Mantrova

doc/src/sgml/config.sgml

@@ -8660,7 +8660,7 @@ LOG:  CleanUpLock: deleting: lock(0xb7acd844) id(24688,24696,0,0,0,1)
     <listitem>
      <para>
       Enables/disables distributed transaction manager based on Clock-SI
-      algorithm. When set to <literal>true</true>, provides cluster-wide
+      algorithm. When set to <literal>true</literal>, provides cluster-wide
       transaction isolation at the <literal>Repeatable Read</literal> level.
      </para>
      <para>