Improve RelationGetIdentityKeyBitmap().
We were using RelationGetIndexList() to update the relation's replica
identity index but instead, we can directly use RelationGetReplicaIndex()
which uses the same functionality. This is a minor code readability
improvement.
Author: Japin Li
Reviewed-By: Takamichi Osumi, Amit Kapila
Discussion: https://postgr.es/m/
4C99A862-69C8-431F-960A-
81B1151F1B89@enterprisedb.com