pgcrypto: Remove explicit hex encoding/decoding from tests
This was from before the hex format was available in bytea. Now we
can remove the extra explicit encoding/decoding calls and rely on the
default output format.
Discussion: https://www.postgresql.org/message-id/flat/
17dcb4f7-7ac1-e2b6-d5f7-
2dfba06cd9ee%40enterprisedb.com