pgsql: Adjust test case added by commit 6136e94dc.

Adjust test case added by commit 6136e94dc.

Per project policy, transient roles created by regression test cases
should be named "regress_something", to reduce the risks of running
such cases against installed servers.  And no such role should ever
be left behind after running a test.

Discussion: https://postgr.es/m/11297.1576868677@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/0af0504da91e5e15f0b203309a1e49a4829dac64

Modified Files
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contrib/postgres_fdw/expected/postgres_fdw.out | 14 +++++++++-----
contrib/postgres_fdw/sql/postgres_fdw.sql      | 15 ++++++++++-----
2 files changed, 19 insertions(+), 10 deletions(-)