[pkg-go] Bug#976820: gitaly: use golang-gopkg-libgit2-git2go.v30

[Pirate Praveen]

Control: forwarded -1 https://gitlab.com/gitlab-org/gitaly/-/issues/2856

On Tue, 8 Dec 2020 10:55:52 +0100 Sebastian Ramacher 
<sramacher at debian.org> wrote:
 > golang-gopkg-libgit2-git2go.v28 will be removed as part of the 
libgit2
 > transition. So please switch to golang-gopkg-libgit2-git2go.v30-dev.

This updated got entangled in another update (licensee gem) which now 
included a new dependency that gitlab does not want to use as per 
https://gitlab.com/gitlab-org/gitaly/-/issues/2856#note_438114315 
though I can't see any new dependency in licensee. I have asked 
upstream for clarification.