Merge bitcoindevkit/bdk#875: Bump bip39 crate to v2.0.0

Merge bitcoindevkit/bdk#875: Bump bip39 crate to v2.0.0

a4647cfa98c300a196cafc5303cc08221d0e23bb Bump bip39 crate to v2.0.0 (Elias Rohrer)

Pull request description:

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  ### Description

  The updated version of `rust-bip39` was just released. It also [bumped the pinned version](https://github.com/rust-bitcoin/rust-bip39/pull/41) of `unicode-normalization`, which previously had lead to some incompatibilities.

  ### Notes to the reviewers

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  of the PR were done in a specific way -->

  ### Changelog notice

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  ### 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:
  rajarshimaitra:
    tACK a4647cfa98c300a196cafc5303cc08221d0e23bb
  notmandatory:
    tACK a4647cfa98c300a196cafc5303cc08221d0e23bb

Tree-SHA512: c13f2c5081cd1cf0477ed41717b09b4854651ee43434760b12a460c19657ec6f437d6401b0b6d32c8315491301d7c9848f0575d427f027adc8390d649fe898a9