pgsql: Fix sepgsql compile error caused by oid removal.

Fix sepgsql compile error caused by oid removal.

Per buildfarm animal rhinoceros. I (Andres) missed replacing a few
uses of ObjectIdAttributeNumber in sepgsql.

It's quite probable that the sepgsql test output will need more
adapting than done in 578b22...

Author: Thomas Munro
Discussion: https://postgr.es/m/CAEepm=2Sk+66HJV8FLDfm_sKTn22j7cWTY_Y1Rok3RxeWL_Y0w@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/937e4e509998de93d5e1c04d312f1b13ef153210

Modified Files
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contrib/sepgsql/database.c | 2 +-
contrib/sepgsql/proc.c     | 4 ++--
contrib/sepgsql/relation.c | 4 ++--
contrib/sepgsql/schema.c   | 2 +-
4 files changed, 6 insertions(+), 6 deletions(-)