Fix deletion of deprecated notes

What does this MR do and why?

Notes in Snippets / Commits are deleted from the DOM even before the user confirmed the deletion. With bootstrap_confirmation_modals enabled this actually caused a bug, because the element is progamatically clicked after confirmation. But as the element is removed from the DOM already, Rails/UJS didn't intercept the click properly.

If we switch from a click handler to an ajax:success handler and remove the note from the DOM after a successful deletion, this problem is resolved.

Closes #355095 (closed)

Screenshots or screen recordings

What	Video
Before w/o bootstrap_confirmation_modals	before-no-ff
Before w/ bootstrap_confirmation_modals	before-ff
After	after

How to set up and validate locally

• (Doesn't matter whether Feature.enable(:bootstrap_confirmation_modals) is enabled or not).
• Visit a commit
• Leave a comment
• Refresh the page
• Try deleting the comment
• Comment is now only removed from page after you confirmed the deletion.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.