XWiki Syntax guide vertical menu links are unexpectedly underlined

The vertical menu on the XWiki Syntax guide has all of its items underlined.

It should be consistent with the similar menu on the user profile.

Right now there's already a CSS rule, but it's quite specific and only targets the user menu:

https://github.com/xwiki/xwiki-platform/blob/c670555edf765828463accc8c69e6b0f9f1912f5/xwiki-platform-core/xwiki-platform-flamingo/xwiki-platform-flamingo-skin/xwiki-platform-flamingo-skin-resources/src/main/resources/flamingo/less/general.less#L182

It should be extended to include all of the vertical menu elements.

Note that after a quick search I could not find the vertical menu component on https://www.xwiki.org/xwiki/bin/view/Documentation/DevGuide/FrontendResources/