Document that autovacuum_max_workers can only be set at server start

per Joshua Tolley

doc/src/sgml/config.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.227 2009/09/11 19:17:03 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.228 2009/09/13 19:52:29 petere Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -3616,8 +3616,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
        <para>
         Specifies the maximum number of autovacuum processes (other than the
         autovacuum launcher) which may be running at any one time.  The default
-        is three.  This parameter can only be set in
-        the <filename>postgresql.conf</> file or on the server command line.
+        is three.  This parameter can only be set at server start.
        </para>
       </listitem>
      </varlistentry>