Merge bitcoindevkit/bdk#2382: docs(file_store): correct Store creation and recovery...

aa60b2dad847e8ff2f0cccf30a3e59c175194c4b docs(file_store): correct Store creation and recovery guidance (luangucun)

Pull request description:

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  ### Description

  Correct two misleading `Store` API comments:

  - `Store::create` opens the file for both reading and writing.
  - Creating a recovered store at an existing path fails; replacing the original file requires a separate operation, as the recovery example demonstrates.

  ### Notes to the reviewers

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

  ### Changelog notice

  <!-- Notice the release manager should include in the release tag message changelog -->
  <!-- See https://keepachangelog.com/en/1.0.0/ for examples -->

  ### Checklists

  #### All Submissions:

  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)

  #### New Features:

  * [ ] I've added tests for the new feature
  * [ ] I've added docs for the new feature

  #### 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

ACKs for top commit:
  evanlinjin:
    ACK aa60b2dad847e8ff2f0cccf30a3e59c175194c4b

Tree-SHA512: e1ec2e8437288c6ec9927b6cde64067bc6ccf25d5c6f8f6824c4e8e874485a95fdefcbdf22424e07df41ee3b20b8d36035849a02e4d3cc599d110a6b197ae77a