pgsql: Fix Subscription test added by commit ce0fdbfe97.

Fix Subscription test added by commit ce0fdbfe97.

We want to test the variants of Alter Subscription that are not allowed in
the transaction block but for that, we don't need to create a subscription
that tries to connect to the publisher. As such, there is no problem with
this test but it is good to allow such tests to run with
wal_level = minimal and max_wal_senders = 0 so as to keep them consistent
with other tests.

Reported by buildfarm.

Author: Amit Kapila
Reviewed-by: Ajin Cherian
Discussion: https://postgr.es/m/CAA4eK1Lw0V+e1JPGHDq=+hVACv=14H8sR+2eJ1k3PEgwKmU-jQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c8b21b0378141948a2dc0ddde6f57407321787ea

Modified Files
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src/test/regress/expected/subscription.out | 6 ++++--
src/test/regress/sql/subscription.sql      | 6 ++++--
2 files changed, 8 insertions(+), 4 deletions(-)