Remove redundant duplicated keys check

This check is redundant since it's already performed by miniscript (see
https://docs.rs/miniscript/7.0.0/miniscript/miniscript/analyzable/enum.AnalysisError.html#variant.RepeatedPubkeys)
and it was incorrectly failing on tr descriptors that contain duplicated
keys across different taproot leaves

Fixes #760

src/descriptor/error.rs

@@ -20,8 +20,6 @@ pub enum Error {
     InvalidDescriptorChecksum,
     /// The descriptor contains hardened derivation steps on public extended keys
     HardenedDerivationXpub,
-    /// The descriptor contains multiple keys with the same BIP32 fingerprint
-    DuplicatedKeys,
 
     /// Error thrown while working with [`keys`](crate::keys)
     Key(crate::keys::KeyError),