build: update to latest btcutil/psbt version

Updates a version of `btcutil/psbt` that has looser parsing requirements
to properly match the BIP.

Fixes: https://github.com/lightningnetwork/lnd/issues/6372

docs/release-notes/release-notes-0.15.0.md

@@ -66,6 +66,8 @@ then watch it on chain. Taproot script spends are also supported through the
 
 * [Fixed node shutdown in forward interceptor itests](https://github.com/lightningnetwork/lnd/pull/6362).
 
+* [Fixed a bug that would cause lnd to be unable to parse certain PSBT blobs](https://github.com/lightningnetwork/lnd/pull/6383).
+
 ## Misc
 
 * [An example systemd service file](https://github.com/lightningnetwork/lnd/pull/6033)