doc: ALTER DOMAIN VALIDATE CONSTRAINT can also fail

Document that ALTER DOMAIN VALIDATE CONSTRAINT can also fail for
composite types.

Report by Ondřej Bouda

doc/src/sgml/ref/alter_domain.sgml

@@ -271,9 +271,9 @@ ALTER DOMAIN <replaceable class="PARAMETER">name</replaceable>
   <title>Notes</title>
 
   <para>
-   Currently, <command>ALTER DOMAIN ADD CONSTRAINT</> and
-   <command>ALTER DOMAIN SET NOT NULL</> will fail if the validated named
-   domain or
+   Currently, <command>ALTER DOMAIN ADD CONSTRAINT</>, <command>ALTER
+   DOMAIN VALIDATE CONSTRAINT</>, and <command>ALTER DOMAIN SET NOT NULL</>
+   will fail if the validated named domain or
    any derived domain is used within a composite-type column of any
    table in the database.  They should eventually be improved to be
    able to verify the new constraint for such nested columns.