pgsql: Set synchronous_commit=on in test_setup.sql.

Set synchronous_commit=on in test_setup.sql.

Starting in cc50080a82 create_index test fails when run with
synchronous_commit=off. synchronous_commit=off delays when hint bits may be
set. Some plans change depending on the number of all-visible pages, which in
turn can be influenced by the delayed hint bits.

Force synchronous_commit to `on` in test_setup.sql. Not very satisfying, but
there's no obvious alternative.

Reported-By: Aleksander Alekseev <aleksander(at)timescale(dot)com>
Author: Andres Freund <andres(at)anarazel(dot)de>
Author: Aleksander Alekseev <aleksander(at)timescale(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/CAJ7c6TPJNof1Q+vJsy3QebgbPgXdu2ErPvYkBdhD6_Ckv5EZRg(at)mail(dot)gmail(dot)com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/02fea8fdda6531f34305b445f92f5b62241329b3

Modified Files
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src/test/regress/expected/test_setup.out | 7 +++++++
src/test/regress/sql/test_setup.sql | 8 ++++++++
2 files changed, 15 insertions(+)