regress: fix test instability

Alvaro Herrera <alvherre@alvh.no-ip.org>

Commit: d2a74621ed0430094e6d1f754df5bc1647408be7
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: 2022-08-05T09:55:52Z
Releases: 13.8
regress: fix test instability

Having additional triggers in a test table made the ORDER BY clauses in
old queries underspecified.  Add another column there for stability.

Per sporadic buildfarm pink.

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