dashboard: remove protocol from google fonts links so they work with htttps

mod/dashboard/app/index.html

@@ -7,8 +7,8 @@
     <title>etcd dashboard</title>
     <meta name="description" content="">
     <meta name="viewport" content="width=device-width">
-    <link href="http://fonts.googleapis.com/css?family=Source+Sans+Pro:200,300,400,400italic,600,700,900" rel="stylesheet" type="text/css">
-    <link href="http://fonts.googleapis.com/css?family=Source+Code+Pro:400,500,600,700" rel="stylesheet" type="text/css">
+    <link href="//fonts.googleapis.com/css?family=Source+Sans+Pro:200,300,400,400italic,600,700,900" rel="stylesheet" type="text/css">
+    <link href="//fonts.googleapis.com/css?family=Source+Code+Pro:400,500,600,700" rel="stylesheet" type="text/css">
     <!-- build:css styles/styles.css -->
     <link rel="stylesheet" href="styles/bootstrap.css">
     <link rel="stylesheet" href="styles/main.css">