Update "Changes" tab count without removing DOM structure

What does this MR do and why?

For #566302 (closed).

Set only the text of the badge, without removing wrappers. This prevents layout thrashing and incorrect width of the badge.

Screenshots or screen recordings

Before	After
simplescreenrecorder-2025-11-12_14.27.19 simplescreenrecorder-2025-11-12_14.27.19.mkv	simplescreenrecorder-2025-11-12_14.26.32 simplescreenrecorder-2025-11-12_14.26.32.mkv

How to set up and validate locally

1. Have an MR with at least one change
2. Go to the Changes tab
3. Note the live update (or refresh the page, if you missed it)

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.