Set a min-height for wiki list items

What does this MR do and why?

Fix item height in wiki sidebar (!115929 - merged) originally fixed an issue where the + button for adding new wiki pages can overrun its container (see screenshots).

That MR was reverted in Revert "Merge branch 'fix-item-height-in-wiki-s... (!124869 - merged) because fixing the height (min and max) created side-effects, where titles >1 line long would run into and overlap each other.

This MR reinstates the intended behavior by using only a min-height. This way, list items will expand to the height of the title without overlapping but will at least be large enough to contain the + button.

Related to Wiki titles on the sidebar overlap if they reac... (#412894 - closed).

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

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

1. Create a wiki in any project.
2. Add one or more pages.
3. Check that the list item in the navbar fully contains the + button when hovered.
4. Create multiple pages with long titles and observe no overlap in list item text.

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.