pgsql: Fix instability in regression test for Parallel Hash Full Join

Fix instability in regression test for Parallel Hash Full Join

As reported by buildfarm member conchuela, one of the regression tests
added by 558c9d7 is having some ordering issues.  This commit adds an
ORDER BY clause to make the output more stable for the problematic
query.

Fix suggested by Tom Lane.  The plan of the query updated still uses a
parallel hash full join.

Author: Melanie Plageman
Discussion: https://postgr.es/m/623596.1684541098@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3e8da50244a8de69317babcfdb048172cf30f14c

Modified Files
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src/test/regress/expected/join_hash.out | 3 ++-
src/test/regress/sql/join_hash.sql      | 3 ++-
2 files changed, 4 insertions(+), 2 deletions(-)