pgsql: Fix instability in recently added regression tests

Fix instability in recently added regression tests

We missed the usual ORDER BY clause.

Author: Amul Sul <amul.sul@enterprisedb.com>
Discussion: https://postgr.es/m/CAAJ_b974U3Vvf-qGwFyZ73DFHqyFJP9TOmuiXR2Kp8KVcJtP6w@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c44c2d2759876463dcbab2eb608e33ed2e772d12

Modified Files
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src/test/regress/expected/foreign_key.out | 15 +++++++++------
src/test/regress/sql/foreign_key.sql      | 15 +++++++++------
2 files changed, 18 insertions(+), 12 deletions(-)