pgsql: Try to stabilize the reloptions test.

Try to stabilize the reloptions test.

Where we test vacuum_truncate's effects, sometimes this is failing to
truncate as expected on the build farm.  That could be explained by page
skipping, so disable it explicitly, with the theory that commit fe246d1c
didn't go far enough.

Back-patch to 12, where the vacuum_truncate tests were added.

Discussion: https://postgr.es/m/CA%2BhUKGLT2UL5_JhmBzUgkdyKfc%3D5J-gJSQJLysMs4rqLUKLAzw%40mail.gmail.com

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/639a9293d4cbf6bdfcc641f335e2c5a2359cce75

Modified Files
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src/test/regress/expected/reloptions.out | 4 ++--
src/test/regress/sql/reloptions.sql      | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)