Merge bitcoindevkit/bdk#1421: fix: Cargo clippy lints

a5fb7fdf505a53b5865ed83d53745e7efa5e7818 fix: Cargo clippy lints after rust 1.78 (Daniela Brozzoni)

Pull request description:

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  ### Description

  Caught when trying to release (#1420), clippy failed randomly although it worked on master, this happened because rust 1.78 had just been release and we use clippy stable. IMHO we should pin the clippy version in CI and bump it manually at each new rust release.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

ACKs for top commit:
  notmandatory:
    ACK a5fb7fdf505a53b5865ed83d53745e7efa5e7818

Tree-SHA512: c803366367576224f9e9690cdee2c0161fc083550355415f9174e93ada2f597440f54ac966bb3ebecdc916824d43de17ac72801e4ef0f75c8a1df640fe40df6d