Initial variant of error message didn't follow style of another casting error
messages and wasn't informative. Per gripe from Robert Haas.

Reviewer: Tom Lane
Discussion: https://www.postgresql.org/message-id/flat/CA%2BTgmob08StTV9yu04D0idRFNMh%2BUoyKax5Otvrix7rEZC8rMw%40mail.gmail.com#CA+Tgmob08StTV9yu04D0idRFNMh+UoyKax5Otvrix7rEZC8rMw@mail.gmail.com