Another 9.1 release note typo fix.

Author: bmomjian

doc/src/sgml/release-9.1.sgml

@@ -1015,7 +1015,7 @@
        Previously asking for serializable isolation produced
        snapshot isolation, which had certain documented anomalies.
        The old snapshot isolation level is still accessible by
-       requesting <link linkend="xact-repeatable-read"><literal>REPEATABLE
+       requesting the <link linkend="xact-repeatable-read"><literal>REPEATABLE
        READ</></link> isolation level.
       </para>
      </listitem>