Revert "Fix top menu dropdown flicker by adding position relative to menu li elements"

This reverts commit c1128f1.

The fix was ineffective because the actual problem is in redmine-base-theme
which sets top: 29px !important on .menu-children, creating a gap.
The proper fix (::before bridge element) has been added to the theme.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: alexandermeindl

assets/stylesheets/additionals.css

@@ -248,11 +248,6 @@ div.macro-desc {
   border-bottom: 1px solid #eee;
 }
 
-/* Dropdown menu - li needs position:relative so .menu-children positions correctly */
-#top-menu > ul > li {
-  position: relative;
-}
-
 #top-menu li:hover ul.menu-children,
 #top-menu li ul.menu-children.visible { display: block; }