git: Bump the minimum version to v2.44

We've set the minimum Git version to 2.42 for quite some time. Since version 2.43, git reads gitattributes(5) from HEAD:.gitattributes for bare repositories. This is something we want to depend on. But since we ship Gitaly with 2.44, bump the minimum version to 2.44 in one go.

Issue: #5882 (closed) Label: maintenance::dependency