React: fix editor cleanup

[kfirmanty]

Please describe your changes

Hi! I noticed that editor.destroy() is not being called for each reference that is being created, this should fix the problem.

How did you accomplish your changes

Cleaning up editor was moved to the return of useEffect that creates a new editor, this way for each editor instantiated there will be a respective cleanup fn.

How have you tested your changes

How can we verify your changes

[add a detailed description of how we can verify your changes here]

Checklist

• The changes are not breaking the editor
• Added tests where possible
• Followed the guidelines
• Fixed linting issues

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[bdbch]

Thanks, lgtm!