Fix tests under wal_level=minimal

Álvaro Herrera <alvherre@kurilemu.de>

Commit: be142fa008ade51bb579a5990b43d55bab743194
Author: Álvaro Herrera <alvherre@kurilemu.de>
Date: 2026-04-07T13:14:32Z
Fix tests under wal_level=minimal

Buildfarm members which have specifically configured to use
wal_level=minimal fail the repack regression tests, which require
wal_level=replica.  Add a temp config file to fix that.

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