Merge bitcoindevkit/bdk#604: unpinning dependency tokio to just 1

939a1156c65d0f347cb4397e0883573737d39761 unpinning dependency tokio to 1 (Richard Ulrich)

Pull request description:

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  ### Description

  unpinning dependency tokio to just 1

  ### 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

  #### New Features:

  * [ ] I've added tests for the new feature
  * [ ] I've added docs for the new feature
  * [x] I've updated `CHANGELOG.md`

  #### Bugfixes:

  * [ ] This pull request breaks the existing API
  * [ ] I've added tests to reproduce the issue which are now passing
  * [ ] I'm linking the issue being fixed by this PR

ACKs for top commit:
  notmandatory:
    ACK 939a1156c65d0f347cb4397e0883573737d39761

Tree-SHA512: 7b33522411f6b63d844d12cc86c8992aa4105c29e91dbef67362a6c600f3ef39e802ff5893054bf8feeb7fa5bf383765025096cbc2ccb9a6b83bc5c919a5a43d