Merge bitcoindevkit/bdk#1299: fix(file_store): rm lifetime from `FileError`

5611c9e42adb4106f48039e19ab0797b266c7fff fix(file_store): rm lifetime from `FileError` (志宇)

Pull request description:

  ### Description

  The lifetime on the error needed to be the same as the input magic bytes which was annoying.

  ### Changelog notice

  Fixed
  * Remove `bdk_file_store::FileError` lifetime.

  ### 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:
  LLFourn:
    ACK 5611c9e42adb4106f48039e19ab0797b266c7fff

Tree-SHA512: 0eca5128c71c9adb10a712d169a2170b8cbb91678f93986957e86b26dbfed3ab19217a136b57328249a13a51cc06e6c424d58683d74a0fa3d29c22af04a95591