pgsql: Doc: Update the documentation for row movement behavior across p

Doc: Update the documentation for row movement behavior across partitions.

In commit f16241bef7c, we have changed the behavior for concurrent updates
that move row to a different partition, but forgot to update the docs.
Previously when an UPDATE command causes a row to move from one partition
to another, there is a chance that another concurrent UPDATE or DELETE
misses this row. However, now we raise a serialization failure error in
such a case.

Reported-by: David Rowley
Author: David Rowley and Amit Kapila
Backpatch-through: 11 where it was introduced
Discussion: https://postgr.es/m/CAKJS1f-iVhGD4-givQWpSROaYvO3c730W8yoRMTF9Gc3craY3w@mail.gmail.com

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/d850af428deb21d074330f6fe801c52e52965fde

Modified Files
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doc/src/sgml/ddl.sgml | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)