Fix spec violation for merge dialog

What does this MR do and why?

This is part of the Vue 3 migration > &5102

• Get rid of spying on methods

Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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

Related to #391098 (closed)