pgsql: Update oidjoins regression test for v11.

Update oidjoins regression test for v11.

Commit 86f575948 already manually updated the oidjoins test for the
new pg_constraint.conparentid => pg_constraint.oid relationship, but
failed to update findoidjoins/README, thus the apparent inconsistency
here.

Michael Paquier

Discussion: /messages/by-id/20180507001811.GA27389@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/fbb99e5883d88687de4dbd832c2843f600ab3dd8

Modified Files
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src/test/regress/expected/oidjoins.out | 8 ++++++++
src/test/regress/sql/oidjoins.sql | 4 ++++
src/tools/findoidjoins/README | 8 +++++---
3 files changed, 17 insertions(+), 3 deletions(-)