fix alert close position

docs/assets/css/bootstrap.css

@@ -2002,6 +2002,7 @@ button.btn.small, input[type="submit"].btn.small {
 }
 .alert .close {
   position: relative;
+  top: -2px;
   right: -21px;
   line-height: 18px;
 }

less/alerts.less

@@ -18,6 +18,7 @@
 // Adjust close link position
 .alert .close {
   position: relative;
+  top: -2px;
   right: -21px;
   line-height: 18px;
 }