pgsql: doc: Mention that toast_tuple_target affects also column marked

doc: Mention that toast_tuple_target affects also column marked as Main.

Previously it was documented that toast_tuple_target affected column
marked as only External or Extended. But this description is not correct
and toast_tuple_target affects also column marked as Main.

Back-patch to v11 where toast_tuple_target reloption was introduced.

Author: Shinya Okano
Reviewed-by: Tatsuhito Kasahara, Fujii Masao
Discussion: https://postgr.es/m/93f46e311a67422e89e770d236059817@oss.nttdata.com

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/72b15740900cb6e0646bcdafabecbaa8eaad9e7e

Modified Files
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doc/src/sgml/ref/create_table.sgml | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)