pgsql: Remove some dead code in selfuncs.c

Remove some dead code in selfuncs.c

RelOptInfo.userid is the same for all relations in a given inheritance
tree, so the code in examine_variable() and example_simple_variable()
that repeats the ACL checks on the root parent rel instead of a given
leaf child relations need not recompute userid too.

Author: Amit Langote <amitlangote09@gmail.com>
Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20221210201753.GA27893@telsasoft.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/438e6b7240905c8055f9e221187f2ac818876169

Modified Files
--------------
src/backend/optimizer/util/relnode.c |  1 -
src/backend/utils/adt/selfuncs.c     | 42 ++++++++++++++----------------------
2 files changed, 16 insertions(+), 27 deletions(-)