Merge bitcoindevkit/bdk#1427: docs(esplora): fixed `full_scan` and `sync` documentation

f6dc6890c37752e80c86c68ae3ca3cc4fac6245e docs(esplora): fixed `full_scan` and `sync` documentation (Wei Chen)

Pull request description:

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  ### Description

  Fixed documentation for `full_scan` and `sync` in `bdk_esplora`.

  ### Changelog notice

  <!-- Notice the release manager should include in the release tag message changelog -->
  <!-- See https://keepachangelog.com/en/1.0.0/ for examples -->
  * Updated documentation for `full_scan` and `sync` in `bdk_esplora`.

  ### 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:
  evanlinjin:
    ACK f6dc6890c37752e80c86c68ae3ca3cc4fac6245e
  storopoli:
    ACK f6dc6890c37752e80c86c68ae3ca3cc4fac6245e

Tree-SHA512: 900fb1a2839379af867a6effad32ec4bdfb897330a72ee1e1ec203299e7f3d5fae576550aeed8fd93c5c70a13ad2b0e898033d8b45b490319b5d74216b93f332