Default to dangerous MR merge button - EE merge edition

See https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9245

Not sure why there is a difference in code here between CE and EE. Seems like the disable logic should be in both areas 😕

• CE: https://gitlab.com/gitlab-org/gitlab-ce/blame/90040620cba77620a57e028d25e6148c72494fbd/app/views/projects/merge_requests/widget/open/_accept.html.haml#L14
• EE: https://gitlab.com/gitlab-org/gitlab-ee/blame/8d61b32eb7b9d20de8e2744ee5171a011ce40ea9/app/views/projects/merge_requests/widget/open/_accept.html.haml#L14