Merge bitcoindevkit/bdk-cli#252: Enforce use of `1.0.0-rc.1` payjoin version

6a2e398686655d5b5538ad17fd82bd8df37690ca fix(dependencies): change payjoin version specifier `1.0.0-rc.1` to `=1.0.0-rc.1` (nymius)

Pull request description:

  **Description**

  Cargo's version resolution always updates to the latest patch version. If that patch introduces breaking changes, it breaks your application.

  This happened after Payjoin released version 1.0.0-rc.2. Because the version specified for bdk-cli was 1.0.0-rc.1, a fresh install automatically updated to the newer patch.

  To resolve this without migrating to the latest Payjoin API, and to prevent future breakages from subsequent 1.0.0-rc.x releases, this commit pins the Payjoin version strictly to =1.0.0-rc.1.

  This happened before in another project: rust-bitcoin/rust-bitcoin#5358

  **Changelog notice**

  ```text
  fix: enforce `1.0.0-rc.1` payjoin version and avoid automatic patch updates
  ```

ACKs for top commit:
  tvpeter:
    ACK 6a2e398686655d5b5538ad17fd82bd8df37690ca

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