Move EE differences for `ready_to_merge.vue`

What does this MR do?

Remove differences for app/assets/javascripts/vue_merge_request_widget/components/states/ready_to_merge.vue component between CE and EE codebase

CE counterpart: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/27587

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Closes #10099 (closed)