Update doc/update/README.md

Originally submitted at
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6004.
Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/update/README.md

@@ -142,4 +142,4 @@ possible.
 [ee-ce]: ../downgrade_ee_to_ce/README.md
 [ce]: https://about.gitlab.com/features/#community
 [ee]: https://about.gitlab.com/features/#enterprise
-[omni-ce-ee]: http://docs.gitlab.com/omnibus/update/README.html#from-community-edition-to-enterprise-edition
+[omni-ce-ee]: https://docs.gitlab.com/omnibus/update/README.html#updating-community-edition-to-enterprise-edition