Resolve conflicts feature does not reset approvals
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### Summary
When clicking "Resolve conflicts" in the GitLab MR widget, the resulting commit does not update the qualified approvers on the MR.
<!-- Summarize the bug encountered concisely. -->
### Steps to reproduce
1. Have user A and user B, and add them to a project
1. Enable "Prevent approvals by users who add commits"
1. Create an MR with conflicts, with all commits belonging to user A
1. As user B, click the "Resolve conflicts" button and resolve conflicts in the GitLab UI
1. Go back to the MR widget and see that user B can still approve the MR
1. Push to the source branch as user A
1. Refresh the MR as user B and see that you _now_ cannot approve the MR
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### Example Project
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behavior, and link to it here in the bug report. If you are using an older version of GitLab, this
will also determine whether the bug is fixed in a more recent version. -->
### What is the current *bug* behavior?
The "Resolve conflicts" button does not reset approvals
<!-- Describe what actually happens. -->
### What is the expected *correct* behavior?
The "Resolve conflicts" button should reset approvals
<!-- Describe what you should see instead. -->
### Possible fixes
I don't think the approval rules are re-assessed unless there's a "push event" for the project on the source branch. When editing a file through an actual git push, through the web IDE, or via the simple "Edit" screen in GitLab, the change will result in a push event. But I've confirmed on my test instance that "Resolve conflicts" does not result in a push event, and will not update the list of committers that can't approve.
I have also confirmed that another "push event" on the source branch will cause the approvals to be re-evaluated. The committers will then be updated in the MR and even the user who only contributed via "Resolve conflicts" will no longer be able to approve.
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issue