Remove wiki sidebar limit and make it scrollable

What does this MR do and why?

Remove wiki sidebar limit

Remove the limit of 15 items in the wiki sidebar

Changelog: changed

MR acceptance checklist

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

Screenshots or screen recordings

Screen Recording 2024-07-02 at 17.01.02.mov

How to set up and validate locally

1. Open a wiki which has more than 15 pages. You can also clone https://gitlab.com/wireshark/wireshark/-/wikis/home and push to your local project's wiki.
2. Observe the sidebar, which now lists all the pages instead of just the first 15.
3. When searching for pages in the sidebar, there isn't a limit either.

Related to #323218 (closed), #415814 (closed)