ui: increase initial timeout to 60s

Failing to fetch the frontend_bundle.js causes a BSOD.
Today the timeout is 20s and frontend_bundle.js is ~4MB.
20s can be too aggressive if the connection is particularly
slow. I've been hitting this myself on flights.
Increasing that to 60s.

Bug: #616
Change-Id: I9ba4d55111ad0a1e3a28147e35b7f0bb3c7b02f6

ui/src/assets/index.html

@@ -49,7 +49,7 @@
   <script type="text/javascript">
     'use strict';
     (function () {
-      const TIMEOUT_MS = 20000;
+      const TIMEOUT_MS = 60000;
       let errTimerId = undefined;
 
       function errHandler(err) {