The implementations of `ThirtyTwoByteHash` for types from the `hashes`
crate are problematic during upgrades because both `bitcoin` and
`secp256k1` depend on `hashes` and when the versions of `hashes` get
out of sync usage of the trait breaks.
Deprecate the `ThirtyTwoByteHash` trait and remove the impls for types
from `bitcoin_hashes`.
Add an explanation in the changelog because its too long to go in the
deprecation message.
9f28cf6ad0