pgsql: Use DELETE instead of UPDATE to speed up vacuum test

Use DELETE instead of UPDATE to speed up vacuum test

01e2b7f0fd02a44e introduced a test which generated dead tuples for
vacuum with an UPDATE. The test only required enough dead TIDs for two
rounds of index vacuuming. This can be accomplished with a DELETE
instead of an UPDATE -- which generates about 50% less WAL and makes the
test 20% faster in many cases. The test takes several seconds (more on
slow buildfarm animals) because we need quite a few tuples to trigger
two rounds of index vacuuming; so it is worth a follow-on commit to
speed it up.

Suggested-by: Masahiko Sawada
Discussion: https://postgr.es/m/CAAKRu_bWmMjmqL%2BOZ2duEQ80u7cRvpsExLNZNjzk-pXX5skwMQ%40mail.gmail.com
Backpatch-through: 14, the first version containing this test.

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/571e0ee40ebdaf0c75b11756620c9c9d453cc644

Modified Files
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src/test/recovery/t/043_vacuum_horizon_floor.pl | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)