Doc: Generated columns are skipped for logical replication.

Add a note in docs that generated columns are skipped for logical
replication.

Author: Peter Smith
Reviewed-by: Peter Eisentraut
Backpatch-through: 12
Discussion: https://postgr.es/m/CAHut+PuXb1GLQztQkoWzYjSwkAZZ0dgCJaAHyJtZF3kmtcL=kA@mail.gmail.com

Author: Amit Kapila

doc/src/sgml/ddl.sgml

@@ -400,6 +400,12 @@ CREATE TABLE people (
       generated columns in <literal>BEFORE</literal> triggers.
      </para>
     </listitem>
+    <listitem>
+     <para>
+      Generated columns are skipped for logical replication and cannot be
+      specified in a <command>CREATE PUBLICATION</command> column list.
+     </para>
+    </listitem>
    </itemizedlist>
   </para>
  </sect1>