Merge bitcoindevkit/bdk#1774: chore[chain,wallet]: fix build warnings

479117c2071a9062438e3b94c2c6cf70ff6fb3c0 chore(chain,wallet): fix build warnings (Steve Myers)

Pull request description:

  ### Description

  fixed #1773

  ### Notes to the reviewers

  I noticed these warnings while publishing beta.6 and would like to get them fixed before the final `bdk_wallet` 1.0.0. With default features we should have any build warnings. To reproduce:

  ```
  cargo build -p bdk_chain
  cargo build -p bdk_wallet
  ```

  ### 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:
  ValuedMammal:
    ACK 479117c2071a9062438e3b94c2c6cf70ff6fb3c0

Tree-SHA512: d9b18f0472ed3a3088c24f46b49361154dd568d95045bee6108a7f6ace84d0da19cfe1079b8549a5ba723e0ded9bca502f0ebf2d557ff4f23ac87ee51e6c335a