Doc: Update the behavior of generated columns in Logical Replication.

Commit 745217a misses updating the new behavior of generated columns in
logical replication at a few places.

Reported-by: Peter Smith, Ajin Cherian
Author: Vignesh C
Discussion: https://postgr.es/m/CALDaNm2JOO7szz9+uaQbjmgZOfzbM_9tAQdFF8H5BjkQeaJs0A@mail.gmail.com
Discussion: https://postgr.es/m/B80D17B2-2C8E-4C7D-87F2-E5B4BE3C069E@gmail.com

Author: Amit Kapila

doc/src/sgml/ddl.sgml

@@ -514,8 +514,9 @@ CREATE TABLE people (
     </listitem>
     <listitem>
      <para>
-      Generated columns are skipped for logical replication and cannot be
-      specified in a <command>CREATE PUBLICATION</command> column list.
+      Generated columns can be replicated during logical replication by
+      including them in the column list of the
+      <command>CREATE PUBLICATION</command> command.
      </para>
     </listitem>
    </itemizedlist>

doc/src/sgml/logical-replication.sgml

@@ -1436,7 +1436,9 @@ test_sub=# SELECT * FROM child ORDER BY a;
    During initial data synchronization, only the published columns are
    copied.  However, if the subscriber is from a release prior to 15, then
    all the columns in the table are copied during initial data synchronization,
-   ignoring any column lists.
+   ignoring any column lists. If the subscriber is from a release prior to 18,
+   then initial table synchronization won't copy generated columns even if they
+   are defined in the publisher.
   </para>
 
    <warning id="logical-replication-col-list-combining">