Merge #69: Fix repl and wallet help docs

3f9b892 Pin fd-lock version to 3.0.2 (Steve Myers)
4a02a9f Manual docs formatting fix (Steve Myers)
c82fd90 Update Cargo.lock (Steve Myers)
81652b1 Fix repl and wallet help docs (Steve Myers)

Pull request description:

  ### Description

  This fixes the help docs for the `repl` and `wallet` subcommands. The `repl` subcommand was showing the proxy options docs instead, and the `wallet` subcommand was showing the description from the `WalletSubCommand` enum.

  This is a workaround for `structopt` issue #333, #391, #418; see TeXitoi/structopt#333 (comment)

  ### Notes to the reviewers

  Before this PR this was showing:
  ```shell
  $ cargo run --features esplora-ureq,compiler -- --help
  ...
  SUBCOMMANDS:
      compile    Compile a miniscript policy to an output descriptor
      help       Prints this message or the help of the given subcommand(s)
      key        Key management sub-commands
      repl       Proxy Server options
      wallet     Wallet sub-commands
  ```

  After this PR we get:
  ```shell
  $ cargo run --features esplora-ureq,compiler -- --help
  ...
  SUBCOMMANDS:
      compile    Compile a miniscript policy to an output descriptor
      help       Prints this message or the help of the given subcommand(s)
      key        Key management sub-commands
      repl       Enter REPL command loop mode
      wallet     Wallet options and sub-commands
  ```

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk-cli/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### 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

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Tree-SHA512: 8d708720f60940edd40826a159388ced261c91d23e074b51164f8c49a2e673cbaecee0241e52cb02090e40ff1f989a980aee0122230cee211f4c3284cad4483c