Don't restyle separators unless they are actually inside PersonalToolbar

Someone might use this style to make the bookmarks toolbar itself
vertical housing buttons etc. but have bookmarks-toolbar-items in some
other horizontal toolbar.

chrome/vertical_bookmarks_toolbar.css

@@ -29,7 +29,7 @@ See the above repository for updates as well as full license text. */
     display: flex;
     flex-direction: column;
   }
-  #PlacesToolbarItems > toolbarseparator{
+  #PersonalToolbar #PlacesToolbarItems > toolbarseparator{
     height: 7px;
     background-color: currentColor;
     background-clip: padding-box;