Bump libgit2-sys from 0.12.25+1.3.0 to 0.12.26+1.3.0

Bumps [libgit2-sys](https://github.com/rust-lang/git2-rs) from 0.12.25+1.3.0 to 0.12.26+1.3.0.
- [Release notes](https://github.com/rust-lang/git2-rs/releases)
- [Commits](https://github.com/rust-lang/git2-rs/commits/libgit2-sys-0.12.26)

---
updated-dependencies:
- dependency-name: libgit2-sys
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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