Remove the `:#` formatting for `hex_fmt_impl` macro

This fixes the issue where pretty debug like `dbg` or `{:#}` introduce the use of
    `0x` prefix to hex encoded transaction ID.

    The transaction id is being forced to pretty print inside the `hex_fmt_impl` macro
    using `{:#}` in the line `write!(f, "{:#}", self)` debug formatter.

    Resolves: #2505

bitcoin/src/blockdata/transaction.rs

@@ -2444,6 +2444,29 @@ mod tests {
         let seq = Sequence::from_seconds_floor(1000);
         println!("{:?}", seq)
     }
+
+    #[test]
+    fn outpoint_format() {
+        let outpoint = OutPoint::default();
+
+        let debug = "OutPoint { txid: 0000000000000000000000000000000000000000000000000000000000000000, vout: 4294967295 }";
+        assert_eq!(debug, format!("{:?}", &outpoint));
+
+        let display = "0000000000000000000000000000000000000000000000000000000000000000:4294967295";
+        assert_eq!(display, format!("{}", &outpoint));
+
+        let pretty_debug = "OutPoint {\n    txid: 0000000000000000000000000000000000000000000000000000000000000000,\n    vout: 4294967295,\n}";
+        assert_eq!(pretty_debug, format!("{:#?}", &outpoint));
+
+        let debug_txid = "0000000000000000000000000000000000000000000000000000000000000000";
+        assert_eq!(debug_txid, format!("{:?}", &outpoint.txid));
+
+        let display_txid = "0000000000000000000000000000000000000000000000000000000000000000";
+        assert_eq!(display_txid, format!("{}", &outpoint.txid));
+
+        let pretty_txid = "0x0000000000000000000000000000000000000000000000000000000000000000";
+        assert_eq!(pretty_txid, format!("{:#}", &outpoint.txid));
+    }
 }
 
 #[cfg(bench)]

hashes/src/util.rs

@@ -39,7 +39,7 @@ macro_rules! hex_fmt_impl(
         impl<$($gen: $gent),*> $crate::_export::_core::fmt::Debug for $ty<$($gen),*> {
             #[inline]
             fn fmt(&self, f: &mut $crate::_export::_core::fmt::Formatter) -> $crate::_export::_core::fmt::Result {
-                write!(f, "{:#}", self)
+                write!(f, "{}", self)
             }
         }
     );