doc: Fix incorrect description of INCLUDING COMMENTS in CREATE FOREIGN TABLE.

doc: Fix incorrect description of INCLUDING COMMENTS in CREATE FOREIGN TABLE.

Commit 302cf157592 added support for LIKE in CREATE FOREIGN TABLE.
In this feature, since indexes are not created for foreign tables,
comments on indexes are not copied either.

However, the documentation incorrectly stated that index comments
would be copied when using INCLUDING COMMENTS. This commit
corrects that by removing the mention of index comments.

Author: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/f86cd84f-a6a3-4451-bae7-5cca9e63b06d@oss.nttdata.com