delete unnecessary codes

src/client/styles/scss/theme/christmas.scss

@@ -205,13 +205,4 @@ html[dark] {
   .grw-navbar {
     background-image: url('/images/themes/christmas/christmas-navbar.jpg');
   }
-
-  .nav-link {
-    border-color: #d7d7d7;
-  }
-
-  .nav-tabs .nav-link.active {
-    background: none;
-    border-color: #d7d7d7;
-  }
 }