Bump github.com/btcsuite/btcd/btcec/v2 to latest version

[jrwbabylonlab]

The github.com/btcsuite/btcd/btcec/v2 v2.3.2 version is currently being used in the Babylon node. However, a newer version, v2.3.4, is available. Given that this is an important dependency, it’s recommended to keep it up to date.

In the API, we had to use replace github.com/btcsuite/btcd/btcec/v2 => github.com/btcsuite/btcd/btcec/v2 v2.3.2 in order to integrate Babylon as a dependency.