Fix failure with textual partition hash keys.
Commit
5e1963fb7 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