removed missing css file

src/views/admin/header.tpl

@@ -7,7 +7,6 @@
 	<link rel="stylesheet" href="{relative_path}/vendor/jquery/css/smoothness/jquery-ui-1.10.4.custom.min.css?{cache-buster}">
 	<link rel="stylesheet" type="text/css" href="{relative_path}/admin.css?{cache-buster}" />
 	<link rel="stylesheet" type="text/css" href="{relative_path}/vendor/mdl/mdl.min.css?{cache-buster}" />
-	<link rel="stylesheet" type="text/css" href="{relative_path}/vendor/snackbar/snackbar.min.css?{cache-buster}" />
 	<link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">
 
 	<script>