Typo fix from IRC breinbaas

doc/src/sgml/release-9.0.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/release-9.0.sgml,v 2.10 2010/03/23 02:28:48 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/release-9.0.sgml,v 2.11 2010/03/23 22:37:14 momjian Exp $ -->
 
 
  <sect1 id="release-9-0">
@@ -814,7 +814,7 @@
               linkend="SQL-CREATETABLE-description"><command>CREATE
               TABLE CONSTRAINT ...  EXCLUDE</></link> clause.  While
               uniqueness checks could be specified using this syntax,
-              the real value of this features is in using complex
+              the real value of this feature is in using complex
               operators that do not have built-in constraints.
             </para>
           </listitem>