Log Message:
py-pygit2: updated to 1.14.0

1.14.0 (2024-01-26)

- Drop support for Python 3.8
- Add Linux wheels for musl on x86_64
- New `Repository.submodules` namespace
- New `Repository.listall_mergeheads()`, `Repository.message`,
  `Repository.raw_message` and `Repository.remove_message()`
- New `pygit2.enums` supersedes the `GIT_` constants
- Now `Repository.status()`, `Repository.status_file()`,
  `Repository.merge_analysis()`, `DiffFile.flags`, `DiffFile.mode`,
  `DiffDelta.flags` and `DiffDelta.status` return enums
- Now repository\'s `merge()`, `merge_commits()` and `merge_trees()`
  take enums/flags for their `favor`, `flags` and `file_flags` arguments.
- Fix crash in filter cleanup
- Documentation fixes