docs about FKs referencing partitioned tables

Hello,

I posted this to the "clean up docs for v12" thread and it was
suggested I make a new thread instead, so here it is. Sorry for the
extra noise! :-)

I noticed the docs at
https://www.postgresql.org/docs/devel/ddl-partitioning.html still say
you can't create a foreign key referencing a partitioned table, even
though the docs for
https://www.postgresql.org/docs/devel/sql-createtable.html have been
updated (compared to v11). My understanding is that foreign keys
*still* don't work as expected when pointing at traditional INHERITS
tables, but they *will* work with declaratively-partitioned tables. In
that case I suggest this change:

diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index a0a7435a03..3b4f43bbad 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -3966,14 +3966,6 @@ ALTER TABLE measurement ATTACH PARTITION
measurement_y2008m02

-      <listitem>
-       <para>
-       While primary keys are supported on partitioned tables, foreign
-       keys referencing partitioned tables are not supported.  (Foreign key
-       references from a partitioned table to some other table are supported.)
-      </para>
-     </listitem>
-
     <listitem>
      <para>
        <literal>BEFORE ROW</literal> triggers, if necessary, must be defined
        on individual partitions, not the partitioned table.
       </para>
@@ -4366,6 +4358,14 @@ ALTER TABLE measurement_y2008m02 INHERIT measurement;
        </para>
       </listitem>

+     <listitem>
+      <para>
+       While primary keys are supported on inheritance-partitioned
tables, foreign
+       keys referencing these tables are not supported.  (Foreign key
+       references from an inheritance-partitioned table to some other
table are supported.)
+      </para>
+     </listitem>
+
       <listitem>
        <para>
         If you are using manual <command>VACUUM</command> or

(I've also attached it as a patch file.) In other words, we should
move this caveat from the section on declaratively-partitioned tables
to the section on inheritance-partitioned tables.

Yours,
Paul