pgsql: doc: clarify which table creation is used for inheritance part.

doc:  clarify which table creation is used for inheritance part.

Previously people might assume that the partition syntax version of
CREATE TABLE is to be used for the inheritance partition table example;
mention that the non-partitioned version should be used.

Reported-by: mib@nic.at

Discussion: https://postgr.es/m/158089540905.1098.15071165437284409576@wrigleys.postgresql.org

Backpatch-through: 10

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/690e4648719183b0527b6c20a87798e5bd6282e4

Modified Files
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doc/src/sgml/ddl.sgml | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)