Merge bitcoindevkit/bdk-cli#253: Add additional slash to show ReceivePayjoin cli...

Merge bitcoindevkit/bdk-cli#253: Add additional slash to show ReceivePayjoin cli docs

a6d22b9af19fdbe212ac8bd7fb1cebd7dc0d0ef5 doc(payjoin): add additional slash to show ReceivePayjoin cli docs (nymius)

Pull request description:

  ### Description

  A missing slash was preventing the `receive_payjoin` command from displaying its documentation string:

  ```bash
  Wallet operations.

  ...
    sync               Syncs with the chosen blockchain server
    broadcast          Broadcasts a transaction to the network. Takes either a raw transaction or a PSBT to extract
    receive_payjoin
    send_payjoin       Sends an original PSBT to a BIP 21 URI and broadcasts the returned Payjoin PSBT
    new_address        Get a new external address
  ...
  ```

  This change adds the additional slash to make a proper doc string, so clap displays it.

ACKs for top commit:
  tvpeter:
    ACK a6d22b9af19fdbe212ac8bd7fb1cebd7dc0d0ef5

Tree-SHA512: 90383ef85fbd0ccbf42b06a5f38a02ec3ed94e817d7cdc1197bc0fe03f2ba3ce77357f65a6fd0b7a787e361db4bc7e38fcb408cafa61e237e098f7fb943afe7b