pgsql: Attempt to fix broken regression test.

Attempt to fix broken regression test.

In commit 8c1d9d56e9a00680a035b8b333a98ea16b121eb7, I attempted to
add a regression test that would fail if the target list was pushed
into a parallel worker, but due to brain fade on my part, it just
randomly fails whether anything bad or not, because the error check
inside the parallel_restricted() function tests whether there is
*any process in the system* that is not connected to a client, not
whether the process running the query is not connected to a client.

A little experimentation has left me pessimistic about the
prospects of doing better here in a short amount of time, so let's
just fall back to checking that the plan is as we expect and leave
the execution-time check for another day.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/103512cee95b5bd0feb83c225eeff61c58874413

Modified Files
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src/test/regress/expected/select_parallel.out | 31 ++-------------------------
src/test/regress/sql/select_parallel.sql | 12 ++---------
2 files changed, 4 insertions(+), 39 deletions(-)