Merge bitcoindevkit/bdk#1955: chore: Update rust-version to 1.86.0

e8c911c464ff7f0d35259cccee0d286c11f04bb2 chore: update rust-version to 1.86.0 (valued mammal)

Pull request description:

  Update `rust-version` to 1.86.0 and address some clippy lints, in particular [`clippy::doc_overindented_list_items`](https://rust-lang.github.io/rust-clippy/master/index.html#doc_overindented_list_items).

  fix #1940

  ### 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:
  evanlinjin:
    re-ACK e8c911c464ff7f0d35259cccee0d286c11f04bb2

Tree-SHA512: e09377f4b31f7da1a74f4cc4b3a7d7f5f7235aac00001adc3cf4b5758efd0383facb367348db2173bd88379259d0d465292d4dd0ab68bc3b61a0bf111b989e7a