Transient failure in `features/project/merge_requests.feature:312`

As seen in https://gitlab.com/gitlab-org/gitlab-ce/builds/15020376.

It seems that we check that the record is closed before asserting something one the page, meaning that if the closing takes longer than expected, the first assertion fails. We should get rid of the first assertion since feature specs shouldn't assert underlying DB data.

See the screenshot that confirms this: