Обсуждение: pgsql: doc: mention pg_upgrade extension script

doc:  mention  pg_upgrade extension script

Since commit e462856a7a, pg_upgrade automatically creates a script to
update extensions, so mention that instead of ALTER EXTENSION.

Backpatch-through: 9.6

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/c3c1fe09e7c34e1abbb0d30e69b7a26abe4d1411

Modified Files
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doc/src/sgml/ref/pgupgrade.sgml | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)