Fix Incorrect Test Description

Unless i'm mistaken, this test is trying to delete an issue not move an issue;

https://gitlab.com/gitlab-org/gitlab/blob/master/spec/requests/api/issues/issues_spec.rb#L835

    context 'when issue does not exist' do
      it 'returns 404 when trying to move an issue' do
        delete api("/projects/#{project.id}/issues/123", user)

        expect(response).to have_gitlab_http_status(404)
      end
    end