psbt: Remove reexport of Prevouts

No idea why this re-export is here, the `Prevouts` type is not even used
in the `psbt` module.

Remove the re-export of `crate::sighash::Prevouts` from `pstb`.

bitcoin/src/psbt/mod.rs

@@ -20,7 +20,6 @@ use crate::blockdata::transaction::{Transaction, TxOut};
 use crate::crypto::ecdsa;
 use crate::crypto::key::{PrivateKey, PublicKey};
 use crate::prelude::*;
-pub use crate::sighash::Prevouts;
 use crate::sighash::{self, EcdsaSighashType, SighashCache};
 use crate::Amount;