Merge branch 'patch-251' into 'master'

Create MR API returns 201 for success

See merge request gitlab-org/gitlab!43838

doc/api/merge_requests.md

@@ -1004,6 +1004,7 @@ order for it to take effect:
    value of zero disables approvals for that project.
 1. The provided value of `approvals_before_merge` must be greater than the
    target project's `approvals_before_merge`.
+1. This API returns 201 (created) for a successful response. 
 
 ```json
 {