Revert "Reset previously set style for lists"

This reverts commit 88df258.

The commit unset a lot of style attributes instead of targeting a
specific conflict with the bootstrap3 template. This broke the menu
styles in many templates, including the default one.

style.less

@@ -2,17 +2,14 @@
 div.plugin__navi {
     li {
         list-style-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFAQMAAAC3obSmAAAAA1BMVEWZmZl86KQWAAAACklEQVQI12OAAwAACgABaQY5MgAAAABJRU5ErkJggg==);
-        all: unset
     }
 
     li.open {
         list-style-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAcAAAAHAQMAAAD+nMWQAAAABlBMVEUAAACZmZl+9SADAAAAAXRSTlMAQObYZgAAABNJREFUeAFj+AeENQwWDAIMQAAAHhICwcrz0MAAAAAASUVORK5CYII=);
-        all: unset
     }
 
     li.close {
         list-style-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAJAQMAAADAY3TdAAAABlBMVEUAAACZmZl+9SADAAAAAXRSTlMAQObYZgAAABZJREFUeAFjZmA+wNwAhiXMGcwBzAsAI6QEKNehQp8AAAAASUVORK5CYII=);
-        all: unset
     }
 
     &.js {