Pub back in deprecated dust_value

When we renamed `dust_value` to `minimal_non_dust` we forgot to keep the
original and deprecated it, doing so assists with the upgrade path.

Pub back in deprecated `dust_value`, linking to the rename.

bitcoin/src/blockdata/script/borrowed.rs

@@ -385,6 +385,12 @@ impl Script {
         }
     }
 
+    /// Returns the minimum value an output with this script should have in order to be
+    /// broadcastable on today’s Bitcoin network.
+    #[deprecated(since = "0.32.0", note = "use minimal_non_dust and friends")]
+    pub fn dust_value(&self) -> crate::Amount { self.minimal_non_dust() }
+
+
     /// Returns the minimum value an output with this script should have in order to be
     /// broadcastable on today's Bitcoin network.
     ///