pgsql: Fix assertion with relation using REPLICA IDENTITY FULL in subsc

Fix assertion with relation using REPLICA IDENTITY FULL in subscriber

In a logical replication subscriber, a table using REPLICA IDENTITY FULL
which has a primary key would try to use the primary key's index
available to scan for a tuple, but an assertion only assumed as correct
the case of an index associated to REPLICA IDENTITY USING INDEX.  This
commit corrects the assertion so as the use of a primary key index is a
valid case.

Reported-by: Dilip Kumar
Analyzed-by: Dilip Kumar
Author: Euler Taveira
Reviewed-by: Michael Paquier, Masahiko Sawada
Discussion: https://postgr.es/m/CAFiTN-u64S5bUiPL1q5kwpHNd0hRnf1OE-bzxNiOs5zo84i51w@mail.gmail.com
Backpatch-through: 10

Branch
------
REL_11_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/70ae82b9b4b5871604ba4e98ebe0f32bef223200

Modified Files
--------------
src/backend/executor/execReplication.c     |  3 ++-
src/test/subscription/t/001_rep_changes.pl | 15 ++++++++++++++-
2 files changed, 16 insertions(+), 2 deletions(-)