Merge branch 'release-version-8' into 'master'

Release GitLab Shell v8.0.0

See merge request gitlab-org/gitlab-shell!218

CHANGELOG

+v8.0.0
+  - SSH certificate support (!207)
+
 v7.2.0
   - Update gitaly-proto to 0.109.0 (!216)
 

VERSION

-7.2.0
+8.0.0