Revert "Silence dead code warnings on InternalRequestError"

This reverts commit 1eacd8a.

Author: spacebear21

payjoin/src/receive/error.rs

@@ -70,12 +70,10 @@ pub(crate) enum InternalRequestError {
     MissingPayment,
     /// The original PSBT transaction fails the broadcast check
     OriginalPsbtNotBroadcastable,
-    #[allow(dead_code)]
     /// The sender is trying to spend the receiver input
     InputOwned(bitcoin::ScriptBuf),
     /// The expected input weight cannot be determined
     InputWeight(crate::psbt::InputWeightError),
-    #[allow(dead_code)]
     /// Original PSBT input has been seen before. Only automatic receivers, aka "interactive" in the spec
     /// look out for these to prevent probing attacks.
     InputSeen(bitcoin::OutPoint),