docs: clearify use of pg_database.datistemplate

Patch by Rajeev rastogi

doc/src/sgml/catalogs.sgml

@@ -2581,10 +2581,10 @@
       <entry><type>bool</type></entry>
       <entry></entry>
       <entry>
-       If true then this database can be used in the
-       <literal>TEMPLATE</literal> clause of <command>CREATE
-       DATABASE</command> to create a new database as a clone of
-       this one
+       If true, then this database can be cloned by
+       any user with <literal>CREATEDB</> privileges;
+       if false, then only superusers or the owner of
+       the database can clone it.
       </entry>
      </row>