update ng/css/gogs.css for the new repo icon
update ng/css/gogs.css for the new repo icon

bringing over PR 1287 from [gogits/gogs](https://github.com/gogits/gogs/pull/1287)
manfer/gitea,nounoursheureux/gitea,manfer/gitea,nounoursheureux/gitea,manfer/gitea,nounoursheureux/gitea