update libgit2 0.20.0 to 0.20.2

Summary:
# Changelog

## 0.20.2 - 2025-05-05
[0.20.1...0.20.2](rust-lang/git2-rs@git2-0.20.1...git2-0.20.2)

### Added

- Added `Status::WT_UNREADABLE`.
  [#1151](rust-lang/git2-rs#1151)

### Fixed

- Added missing codes for `GIT_EDIRECTORY`, `GIT_EMERGECONFLICT`, `GIT_EUNCHANGED`, `GIT_ENOTSUPPORTED`, and `GIT_EREADONLY` to `Error::raw_code`.
  [#1153](rust-lang/git2-rs#1153)
- Fixed missing initialization in `Indexer::new`.
  [#1160](rust-lang/git2-rs#1160)

## 0.20.1 - 2025-03-17
[0.20.0...0.20.1](rust-lang/git2-rs@git2-0.20.0...git2-0.20.1)

### Added

- Added `Repository::branch_upstream_merge()`
  [#1131](rust-lang/git2-rs#1131)
- Added `Index::conflict_get()`
  [#1134](rust-lang/git2-rs#1134)
- Added `Index::conflict_remove()`
  [#1133](rust-lang/git2-rs#1133)
- Added `opts::set_cache_object_limit()`
  [#1118](rust-lang/git2-rs#1118)
- Added `Repo::merge_file_from_index()` and associated `MergeFileOptions` and `MergeFileResult`.
  [#1062](rust-lang/git2-rs#1062)

### Changed

- The `url` dependency minimum raised to 2.5.4
  [#1128](rust-lang/git2-rs#1128)
- Changed the tracing callback to abort the process if the callback panics instead of randomly detecting the panic in some other function.
  [#1121](rust-lang/git2-rs#1121)
- Credential helper config (loaded with `CredentialHelper::config`) now checks for helpers that start with something that looks like an absolute path, rather than checking for a `/` or `\` anywhere in the helper string (which resolves an issue if the helper had arguments with `/` or `\`).
  [#1137](rust-lang/git2-rs#1137)

### Fixed

- Fixed panic in `Remote::url_bytes` if the url is empty.
  [#1120](rust-lang/git2-rs#1120)
- Fixed incorrect lifetimes on `Patch::delta`, `Patch::hunk`, and `Patch::line_in_hunk`. The return values must not outlive the `Patch`.
  [#1141](rust-lang/git2-rs#1141)
- Bumped requirement to libgit2-sys 0.18.1, which fixes linking of advapi32 on Windows.
  [#1143](rust-lang/git2-rs#1143)

ignore-conflict-markers

Reviewed By: JakobDegen

Differential Revision: D74659779

fbshipit-source-id: a18bcd8f58bc62c7eedbfa5939a791002e18d7bc

Author: Carlos Fernandez