Update libgit2 to 0.24.3
Update libgit2 to 0.24.3

Version 0.24.3 is the latest release version of libgit2, and also includes a fix for "non-modular header" errors:
https://github.com/libgit2/libgit2/commit/0370dae1adea43f250b66abb0d48f9cc5987c15a

SwiftGit2/SwiftGit2,mattrubin/SwiftGit2,mattrubin/SwiftGit2,SwiftGit2/SwiftGit2