Commit 5e1963fb overlooked two places in partbounds.c that now
need to pass a collation identifier to the hash functions for
a partition key column.

Amit Langote, per report from Jesper Pedersen

Discussion: https://postgr.es/m/a620f85a-42ab-e0f3-3337-b04b97e2e2f5@redhat.com