fix 7.14 stable branch name

doc/update/6.x-or-7.x-to-7.14.md

@@ -162,7 +162,7 @@ sudo cp lib/support/init.d/gitlab /etc/init.d/gitlab
 TIP: to see what changed in `gitlab.yml.example` in this release use next command:
 
 ```
-git diff 6-0-stable:config/gitlab.yml.example 7.14-stable:config/gitlab.yml.example
+git diff 6-0-stable:config/gitlab.yml.example 7-14-stable:config/gitlab.yml.example
 ```
 
 * Make `/home/git/gitlab/config/gitlab.yml` the same as https://gitlab.com/gitlab-org/gitlab-ce/blob/7-14-stable/config/gitlab.yml.example but with your settings.