Approving a Merge Request shows as "Opened a Merge Request" in the Activity-Tab

Summary

The Action of approving a Merge Request is shown as "Opened a Merge Request" in the Activity-Tab of the corresponding project.

Steps to reproduce

Create a new branch with some changes
Create a Merge Request with this branch
Approve the Merge Request
Change to the Activity-Tab, it will show two events of type "opened merge request ! "" "

Example Project

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What is the current bug behavior?

A wrong event is shown in the Activity-Tab.

What is the expected correct behavior?

The event should state that the person approved the merge request, not opened it.

Relevant logs and/or screenshots

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Output of checks

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Results of GitLab environment info

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`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

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sudo gitlab-rake gitlab:check SANITIZE=true)
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sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

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