pgsql: doc: Mention validation attempt during ALTER INDEX .. ATTACH PAR

doc: Mention validation attempt during ALTER INDEX .. ATTACH PARTITION

Since 9d3e094f12, the command tries to validate the parent index of the
named index, if invalid. The documentation did not mention this
behavior, which could be confusing.

Author: Mohamed ALi <moali.pg@gmail.com>
Discussion: /messages/by-id/CAGnOmWpHu25_LpT=zv7KtetQhqV1QEZzFYLd_TDyOLu1Od9fpw@mail.gmail.com
Backpatch-through: 14

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/e4f035de455e54653a811fda35d1458ec73def60

Modified Files
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doc/src/sgml/ref/alter_index.sgml | 5 +++++
1 file changed, 5 insertions(+)