Menus: Bring back line break between menu items.

While removing line breaks was great for all use cases except justified menu
items, it broke menus with justified menu items.
Reverts [34321].

Props wp-architect.
Fixes #35107.



git-svn-id: https://develop.svn.wordpress.org/trunk@36081 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/nav-menu-template.php

@@ -211,7 +211,7 @@ class Walker_Nav_Menu extends Walker {
 	 * @param array  $args   An array of arguments. @see wp_nav_menu()
 	 */
 	public function end_el( &$output, $item, $depth = 0, $args = array() ) {
-		$output .= '</li>';
+		$output .= "</li>\n";
 	}
 
 } // Walker_Nav_Menu