RE: Documentation to upgrade logical replication cluster

Dear Vignesh,

Thanks for updating the patch! Basically your patch looks good.
Below lines are my comments for v3.

01.

```
<para>
The output plugins referenced by the slots on the old cluster must be
installed in the new PostgreSQL executable directory.
</para>
```

PostgreSQL must be marked as <productname>.

02.

```
<programlisting>
pg_ctl -D /opt/PostgreSQL/data1 stop -l logfile
</programlisting>
```

I checked that found that -l was no-op when `pg_ctl stop` was specified. Can we remove?
The documentation is not listed -l for the stop command.
All the similar lines should be fixed as well.

03.

```
On <literal>node3</literal>, create any tables that were created in
the upgraded <literal>node2</literal> between
<xref linkend="cascaded-cluster-disable-sub-node2-node3"/> and now,
```

If tables are newly defined on node1 between 1 - 11, they are not defined on node3.
So they must be defined on node3 as well.

04.

```
<step>
<para id="cascaded-cluster-disable-sub-node2-node3">
```

Even if the referred steps is correct, ID should be allocated to step, not para.
That's why the rendering is bit a strange.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED