2 events created when creating a merge request

Summary

When a new MR is created 2 same events are created instead of 1

Steps to reproduce

1. create a new MR
2. check your feed

What is the current bug behavior?

2 same events are created

What is the expected correct behavior?

1 event is created

Possible fixes

This is caused by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13326/diffs#20e62aa0961d84e8c2c96024cd145cceeead6bf4_22_29 - we moved event creation from the issue and merge request create services to workers but forgot to remove the creation of an event from merge request service. It is ok for issues (we did it correctly there), only MRs are the problem.

We need to remove the creation of an event from the service