pgsql: Remove unused field from SubPlanState struct

Remove unused field from SubPlanState struct

bf6c614a2 did some conversion work to use ExprState instead of manually
calling equality functions to check if one set of values is not distinct
from another set. That patch removed many of the fields that became
redundant as a result of that change, but it forgot to remove
SubPlanState.tab_eq_funcs. Fix that.

In passing, fix the header comment for TupleHashEntryData to correctly
spell the field name it's talking about.

Author: Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com>
Reviewed-by: Andrei Lepikhov <lepihov(at)gmail(dot)com>
Discussion: https://postgr.es/m/CA+FpmFeycdombFzrjZw7Rmc29CVm4OOzCWwu=dVBQ6q=PX8SvQ@mail.gmail.com
Discussion: https://postgr.es/m/CAApHDvrWR2jYVhec=COyF2g2BE_ns91NDsCHAMFiXbyhEujKdQ@mail.gmail.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/3974bc319639ad7da5934ba8d04d474a6f7fdee6

Modified Files
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src/backend/executor/nodeSubplan.c | 4 ----
src/include/nodes/execnodes.h | 3 +--
2 files changed, 1 insertion(+), 6 deletions(-)