Failing to edit a comment in the changes tab, updates the comment in the doscussions tab
### Summary
When the API returns an error the comment gets updated in the discussions tab.
### Steps to reproduce
1. Go to a MR
1. Click on the `Changes` tab
1. Click the the edit button to edit a comment
1. Edit the comment
1. Toggle the offline feature in the inspector panel
1. Click save comment
1. Click on the `Discussion` tab
1. See the updated comment
### What is the expected *correct* behaviour?
The comment should not be updated in the `Discussion` tab.
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