Use GitLab internal link instead of third-party hosting on docs

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

doc/user/project/repository/git_blame.md

@@ -8,7 +8,7 @@ description: "Documentation on Git file blame."
 
 # Git file blame
 
-> [Introduced](https://git.sphere.ly/staff/publicgitlab/commit/39c657930625ddc3ac8a921f01ffc83acadce68f) in GitLab 2.5
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/commit/39c657930625ddc3ac8a921f01ffc83acadce68f) in GitLab 2.5.
 
 [Git blame](https://git-scm.com/docs/git-blame) provides more information
 about every line in a file, including the last modified time, author, and