Fix typo.

Reported by KOIZUMI Satoru.

Author: tatsuo-ishii

doc/src/sgml/datatype.sgml

@@ -4727,7 +4727,7 @@ SELECT * FROM pg_attribute
 
        <row>
         <entry><type>pg_ddl_command</></entry>
-        <entry>Identifies a represention of DDL commands that is available to event triggers.</entry>
+        <entry>Identifies a representation of DDL commands that is available to event triggers.</entry>
        </row>
 
        <row>