Fix typo.

Noriyoshi Shinoda

Discussion: http://postgr.es/m/DM4PR84MB17347D9466419413698105D8EE6F2@DM4PR84MB1734.NAMPRD84.PROD.OUTLOOK.COM

Author: robertmhaas

doc/src/sgml/ref/pg_walsummary.sgml

@@ -58,7 +58,7 @@ PostgreSQL documentation
     <variablelist>
      <varlistentry>
       <term><option>-i</option></term>
-      <term><option>--indivudual</option></term>
+      <term><option>--individual</option></term>
       <listitem>
        <para>
         By default, <literal>pg_walsummary</literal> prints one line of output