package/libgit2: bump version to 1.9.0
For release note, see:
https://github.com/libgit2/libgit2/releases/tag/v1.9.0
Signed-off-by: Nicolas Cavallari <nicolas.cavallari@green-communications.fr>
[Julien: add link to release note]
Signed-off-by: Julien Olivain <ju.o@free.fr>