pgsql: Fix unstable regression test results.

Fix unstable regression test results.

Commit 2ac3ef7a0 added a query with an underdetermined output row order;
it has failed multiple times in the buildfarm since then. Add an ORDER BY
to fix. Also, don't rely on a DROP CASCADE to drop in a well-determined
order; that hasn't failed yet but I don't trust it much, and we're not
saving any typing by using CASCADE anyway.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/257d8157205a7be5f9799e8941b922521d678a25

Modified Files
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src/test/regress/expected/insert.out | 8 +++-----
src/test/regress/sql/insert.sql | 5 +++--
2 files changed, 6 insertions(+), 7 deletions(-)