`native.git_repo_root` should have a parameter limiting how far up it can go

[yshui]

when called from

https://github.com/saghen/blink.cmp/blob/05fd5da399a9e3a559ba2585d70c17a8f50a4471/lua/blink/cmp/init.lua#L8-L13

the search for .git should not go up more than 3 levels, because then what you get won't be the git repository of blink-cmp.

found this because i am not running blink-cmp for its git repository, so it instead used the git repository in my /home/user...